Refactor IMAP sync caching and improve thread safety

Replaced `IMemoryCache` with a thread-safe `ConcurrentDictionary`
for managing IMAP sync dates in `LimilabsImapEmailService`. Added
`GetLastImapSyncDate` and `SetLastImapSyncDate` methods to handle
cache operations. Updated the `IImapEmailService` interface to
include `GetLastImapSyncDate`. Simplified the `MarkAsSeenAsync`
method signature for better readability. Introduced a private
record type `ImapCacheKey` to encapsulate cache keys.

.gitignore

@@ -371,3 +371,5 @@ FodyWeavers.xsd
 /EnvelopeGenerator.Server/EnvelopeGenerator.Server/tekh_softHSM_test.md
 /legacy/App
 /src/DigitalData.MessagingService.API/appsettings.Secrets.json
+/src/presentation/DigitalData.MessagingService.API/appsettings.Secrets.json
+/src/presentation/DigitalData.MessagingService.API/appsettings.Secrets.json

AGENTS.md

@@ -330,7 +330,7 @@ return Accepted(); // HTTP 202 - command queued for processing
                arguments: null);
        }
        
-       public async Task EnqueueAsync(OutgoingEmail email, CancellationToken cancellationToken)
+       public async Task EnqueueAsync(SendingEmail email, CancellationToken cancellationToken)
        {
            var json = JsonSerializer.Serialize(email);
            var body = Encoding.UTF8.GetBytes(json);
@@ -347,7 +347,7 @@ return Accepted(); // HTTP 202 - command queued for processing
            await Task.CompletedTask;
        }
        
-       public async Task<OutgoingEmail?> DequeueAsync(CancellationToken cancellationToken)
+       public async Task<SendingEmail?> DequeueAsync(CancellationToken cancellationToken)
        {
            var result = _channel.BasicGet(QueueName, autoAck: false);
            
@@ -355,7 +355,7 @@ return Accepted(); // HTTP 202 - command queued for processing
                return null;
            
            var json = Encoding.UTF8.GetString(result.Body.ToArray());
-           var email = JsonSerializer.Deserialize<OutgoingEmail>(json);
+           var email = JsonSerializer.Deserialize<SendingEmail>(json);
            
            _channel.BasicAck(result.DeliveryTag, false);
            

DigitalData.MessagingService.sln

@@ -27,18 +27,16 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "DigitalData.MessagingServic
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "DigitalData.MessagingService.Domain", "src\core\DigitalData.MessagingService.Domain\DigitalData.MessagingService.Domain.csproj", "{8E44FA5B-43DD-E273-C682-FC382A854A6D}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "DigitalData.MessagingService.Publisher.Abstraction", "src\core\DigitalData.MessagingService.Publisher.Abstraction\DigitalData.MessagingService.Publisher.Abstraction.csproj", "{8A44EE33-02AA-8B3F-60F7-91BA483740A9}"
-EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "DigitalData.MessagingService.Infrastructure", "src\infrastructure\DigitalData.MessagingService.Infrastructure\DigitalData.MessagingService.Infrastructure.csproj", "{56607AAB-3DEC-CB78-3062-56A8EEF5E9D2}"
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "DigitalData.MessagingService.RabbitMQ", "src\infrastructure\DigitalData.MessagingService.RabbitMQ\DigitalData.MessagingService.RabbitMQ.csproj", "{4CF993A6-FA3E-CBF7-C4CB-FFAEBFCFF705}"
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "DigitalData.MessagingService.API", "src\presentation\DigitalData.MessagingService.API\DigitalData.MessagingService.API.csproj", "{8BF22107-3CB9-C326-B94B-C40C99DA9B68}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "DigitalData.MessagingService.Client.DependencyInjection", "src\presentation\DigitalData.MessagingService.Client.DependencyInjection\DigitalData.MessagingService.Client.DependencyInjection.csproj", "{B67C6FA8-DA47-41EC-B15A-511C5B19C036}"
-EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "DigitalData.MessagingService.Publisher", "src\infrastructure\DigitalData.MessagingService.Publisher\DigitalData.MessagingService.Publisher.csproj", "{8DBBAA7C-C4D3-4ADD-8372-B0D6260C8FFC}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "DigitalData.MessagingService.Client", "src\presentation\DigitalData.MessagingService.Client\DigitalData.MessagingService.Client.csproj", "{770E96B0-C3C9-A9A3-4F98-F7A0295D1599}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -57,10 +55,6 @@ Global
 		{8E44FA5B-43DD-E273-C682-FC382A854A6D}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{8E44FA5B-43DD-E273-C682-FC382A854A6D}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{8E44FA5B-43DD-E273-C682-FC382A854A6D}.Release|Any CPU.Build.0 = Release|Any CPU
-		{8A44EE33-02AA-8B3F-60F7-91BA483740A9}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{8A44EE33-02AA-8B3F-60F7-91BA483740A9}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{8A44EE33-02AA-8B3F-60F7-91BA483740A9}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{8A44EE33-02AA-8B3F-60F7-91BA483740A9}.Release|Any CPU.Build.0 = Release|Any CPU
 		{56607AAB-3DEC-CB78-3062-56A8EEF5E9D2}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{56607AAB-3DEC-CB78-3062-56A8EEF5E9D2}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{56607AAB-3DEC-CB78-3062-56A8EEF5E9D2}.Release|Any CPU.ActiveCfg = Release|Any CPU
@@ -73,14 +67,14 @@ Global
 		{8BF22107-3CB9-C326-B94B-C40C99DA9B68}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{8BF22107-3CB9-C326-B94B-C40C99DA9B68}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{8BF22107-3CB9-C326-B94B-C40C99DA9B68}.Release|Any CPU.Build.0 = Release|Any CPU
-		{B67C6FA8-DA47-41EC-B15A-511C5B19C036}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{B67C6FA8-DA47-41EC-B15A-511C5B19C036}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{B67C6FA8-DA47-41EC-B15A-511C5B19C036}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{B67C6FA8-DA47-41EC-B15A-511C5B19C036}.Release|Any CPU.Build.0 = Release|Any CPU
 		{8DBBAA7C-C4D3-4ADD-8372-B0D6260C8FFC}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{8DBBAA7C-C4D3-4ADD-8372-B0D6260C8FFC}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{8DBBAA7C-C4D3-4ADD-8372-B0D6260C8FFC}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{8DBBAA7C-C4D3-4ADD-8372-B0D6260C8FFC}.Release|Any CPU.Build.0 = Release|Any CPU
+		{770E96B0-C3C9-A9A3-4F98-F7A0295D1599}.Debug|Any CPU.ActiveCfg = Release|Any CPU
+		{770E96B0-C3C9-A9A3-4F98-F7A0295D1599}.Debug|Any CPU.Build.0 = Release|Any CPU
+		{770E96B0-C3C9-A9A3-4F98-F7A0295D1599}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{770E96B0-C3C9-A9A3-4F98-F7A0295D1599}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -92,12 +86,11 @@ Global
 		{71BEA4D0-7835-4A8C-B11E-1088E0801DCE} = {02EA681E-C7D8-13C7-8484-4AC65E1B71E8}
 		{7CBE8648-F259-CC91-87FF-5859280867A8} = {DD9D4A3A-AB55-456E-80D3-54A2D4025E64}
 		{8E44FA5B-43DD-E273-C682-FC382A854A6D} = {DD9D4A3A-AB55-456E-80D3-54A2D4025E64}
-		{8A44EE33-02AA-8B3F-60F7-91BA483740A9} = {DD9D4A3A-AB55-456E-80D3-54A2D4025E64}
 		{56607AAB-3DEC-CB78-3062-56A8EEF5E9D2} = {71BEA4D0-7835-4A8C-B11E-1088E0801DCE}
 		{4CF993A6-FA3E-CBF7-C4CB-FFAEBFCFF705} = {71BEA4D0-7835-4A8C-B11E-1088E0801DCE}
 		{8BF22107-3CB9-C326-B94B-C40C99DA9B68} = {B52B4CEE-1C67-424B-8659-370FEA7EAF2A}
-		{B67C6FA8-DA47-41EC-B15A-511C5B19C036} = {B52B4CEE-1C67-424B-8659-370FEA7EAF2A}
 		{8DBBAA7C-C4D3-4ADD-8372-B0D6260C8FFC} = {71BEA4D0-7835-4A8C-B11E-1088E0801DCE}
+		{770E96B0-C3C9-A9A3-4F98-F7A0295D1599} = {B52B4CEE-1C67-424B-8659-370FEA7EAF2A}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {90E29FDC-F6C6-414F-94BF-25DF61D18060}

src/core/DigitalData.MessagingService.Application/Common/Dto/EmailAccounts/EmailAccountDto.cs

@@ -0,0 +1,46 @@
+namespace DigitalData.MessagingService.Application.Common.Dto.EmailAccounts;
+
+/// <summary>
+/// DTO for a single email account configuration.
+/// </summary>
+public record EmailAccountDto
+{
+    /// <summary>
+    /// Logical name to identify this account (e.g. "default", "support").
+    /// </summary>
+    public int Id { get; set; }
+
+#if NET
+    public required string Username { get; set; }
+#else
+    public string Username { get; set; } = null!;
+#endif
+
+#if NET
+    public required string SmtpServer { get; set; }
+#else
+    public string SmtpServer { get; set; } = null!;
+#endif
+
+    public int SmtpPort { get; set; }
+
+    public bool SmtpUseSsl { get; set; }
+
+    public bool UseOAuth2 { get; set; }
+
+    /// <summary>
+    /// IMAP server hostname (e.g. "imap.example.com").
+    /// Leave empty when this account is send-only.
+    /// </summary>
+    public string? ImapServer { get; set; }
+
+    /// <summary>
+    /// IMAP server port (993 for SSL, 143 for plain/STARTTLS).
+    /// </summary>
+    public int ImapPort { get; set; } = 993;
+
+    /// <summary>
+    /// Use SSL/TLS when connecting to the IMAP server.
+    /// </summary>
+    public bool ImapUseSsl { get; set; } = true;
+}

src/core/DigitalData.MessagingService.Application/Common/Dto/EmailAccounts/EmailAccountModificationDto.cs

@@ -0,0 +1,47 @@
+namespace DigitalData.MessagingService.Application.Common.Dto.EmailAccounts;
+
+/// <summary>
+/// DTO for a single email account configuration.
+/// </summary>
+public record EmailAccountModificationDto
+{
+#if NET
+    public required string Username { get; set; }
+#else
+    public string Username { get; set; } = null!;
+#endif
+
+#if NET
+    public required string Password { get; set; }
+#else
+    public string Password { get; set; } = null!;
+#endif
+
+#if NET
+    public required string SmtpServer { get; set; }
+#else
+    public string SmtpServer { get; set; } = null!;
+#endif
+
+    public int SmtpPort { get; set; }
+
+    public bool SmtpUseSsl { get; set; }
+
+    public bool UseOAuth2 { get; set; }
+
+    /// <summary>
+    /// IMAP server hostname (e.g. "imap.example.com").
+    /// Leave empty when this account is send-only.
+    /// </summary>
+    public string? ImapServer { get; set; }
+
+    /// <summary>
+    /// IMAP server port (993 for SSL, 143 for plain/STARTTLS).
+    /// </summary>
+    public int ImapPort { get; set; } = 993;
+
+    /// <summary>
+    /// Use SSL/TLS when connecting to the IMAP server.
+    /// </summary>
+    public bool ImapUseSsl { get; set; } = true;
+}

src/core/DigitalData.MessagingService.Application/Common/Dto/EmailAttachmentDto.cs

@@ -0,0 +1,45 @@
+namespace DigitalData.MessagingService.Application.Common.Dto;
+
+/// <summary>
+/// Represents a single email attachment.
+/// </summary>
+public sealed class EmailAttachmentDto
+{
+    /// <summary>
+    /// Display name of the attachment (e.g. "invoice.pdf").
+    /// </summary>
+#if NETFRAMEWORK
+    public string FileName { get; set; } = null!;
+#else
+    public required string FileName { get; init; }
+#endif
+
+    /// <summary>
+    /// Raw content of the attachment.
+    /// </summary>
+#if NETFRAMEWORK
+    public byte[] Content { get; set; } = null!;
+#else
+    public required byte[] Content { get; init; }
+#endif
+
+    /// <summary>
+    /// MIME content-type (e.g. "application/pdf", "image/png").
+    /// Defaults to "application/octet-stream" when not specified.
+    /// </summary>
+    public string ContentType { get; set; } = "application/octet-stream";
+
+    /// <summary>
+    /// When <see langword="true"/> the attachment is embedded inline and displayed
+    /// directly inside the email body via a CID reference (e.g. &lt;img src="cid:logo"&gt;).
+    /// When <see langword="false"/> (default) it appears as a regular downloadable attachment.
+    /// </summary>
+    public bool IsInline { get; set; } = false;
+
+    /// <summary>
+    /// Content-ID used when <see cref="IsInline"/> is <see langword="true"/>.
+    /// Reference it in HTML body as <c>cid:{ContentId}</c>.
+    /// Auto-generated from <see cref="FileName"/> when left empty.
+    /// </summary>
+    public string? ContentId { get; set; }
+}

src/core/DigitalData.MessagingService.Application/Common/Dto/EmailContext.cs

@@ -0,0 +1,57 @@
+using DigitalData.MessagingService.Domain.Entities;
+
+namespace DigitalData.MessagingService.Application.Common.Dto;
+
+public record EmailContext
+{
+#if NETFRAMEWORK
+    public EmailAccount Sender { get; set; } = null!;
+#else
+    public required EmailAccount Sender { get; init; }
+#endif
+
+    /// <summary>
+    /// Recipient email address
+    /// </summary>
+
+#if NETFRAMEWORK
+    public IEnumerable<string> Recipients { get; set; } = null!;
+#else
+    public required IEnumerable<string> Recipients { get; init; }
+#endif
+
+    /// <summary>
+    /// Email subject
+    /// </summary>
+
+#if NETFRAMEWORK
+    public string Subject { get; set; } = null!;
+#else
+    public required string Subject { get; init; }
+#endif
+
+    /// <summary>
+    /// Email body (HTML or plain text)
+    /// </summary>
+#if NETFRAMEWORK
+    public string Body { get; set; } = null!;
+#else
+    public required string Body { get; init; }
+#endif
+
+    /// <summary>
+    /// Is HTML email (default: true)
+    /// </summary>
+#if NETFRAMEWORK
+    public bool IsHtml { get; set; } = true;
+#else
+    public bool IsHtml { get; init; } = true;
+#endif
+
+    /// <summary>
+    /// Optional list of attachments to include with the email.
+    /// Each entry may carry its content as a byte array (<see cref="EmailAttachmentDto.Content"/>)
+    /// or reference a file on disk via <see cref="EmailAttachmentDto.FilePath"/>.
+    /// </summary>
+    public IEnumerable<EmailAttachmentDto> Attachments { get; set; } = [];
+}

src/core/DigitalData.MessagingService.Application/Common/Dto/EmailSyncResult.cs

@@ -0,0 +1,5 @@
+#if NET
+namespace DigitalData.MessagingService.Application.Common.Dto;
+
+public record EmailSyncResult(int ProcessedCount = 0, int FailedCount = 0);
+#endif

src/core/DigitalData.MessagingService.Application/Common/Dto/MailSearch/DateFilter.cs

@@ -0,0 +1,15 @@
+#if NET
+namespace DigitalData.MessagingService.Application.Common.Dto.MailSearch;
+
+/// <summary>
+/// Constrains the search to messages within an arrival-date range.
+/// </summary>
+/// <remarks>
+/// At least one of <see cref="After"/> or <see cref="Before"/> must be provided.
+/// When both are set <see cref="After"/> must be earlier than <see cref="Before"/>.
+/// Both bounds are <b>inclusive</b>.
+/// </remarks>
+/// <param name="After">Earliest date to include (inclusive). Maps to IMAP <c>SINCE</c>.</param>
+/// <param name="Before">Latest date to include (inclusive). Maps to IMAP <c>BEFORE</c> (next day is used internally).</param>
+public record DateFilter(DateTime? After = null, DateTime? Before = null);
+#endif

src/core/DigitalData.MessagingService.Application/Common/Dto/MailSearch/MailSearchFilter.cs

@@ -0,0 +1,80 @@
+#if NET
+namespace DigitalData.MessagingService.Application.Common.Dto.MailSearch;
+
+/// <summary>
+/// Describes all criteria and options used when searching an IMAP mailbox.
+/// </summary>
+/// <remarks>
+/// All text-match properties are <b>case-insensitive</b> substring searches performed server-side via IMAP SEARCH.
+/// Combine multiple criteria freely; an implicit AND is applied across all non-null fields.
+/// </remarks>
+public record MailSearchFilter
+{
+    /// <summary>
+    /// Mailbox folder to search. Defaults to <c>"INBOX"</c>.
+    /// </summary>
+    public string Folder { get; init; } = "INBOX";
+
+    /// <summary>
+    /// When <see langword="true"/>, only unread (UNSEEN) messages are returned.
+    /// </summary>
+    public bool UnseenOnly { get; init; } = false;
+
+    /// <summary>
+    /// When <see langword="true"/>, attachment data is included in the results; otherwise attachments are omitted.
+    /// Defaults to <see langword="false"/>.
+    /// </summary>
+    public bool WithAttachments { get; init; } = false;
+
+    /// <summary>
+    /// Maximum number of messages to retrieve. <c>0</c> means unlimited.
+    /// Applied after sorting; defaults to <c>50</c>.
+    /// </summary>
+    public int? MaxCount { get; init; } = null;
+
+    /// <summary>
+    /// Controls the order of the returned messages. Defaults to <see cref="MailSortOrder.NewestFirst"/>.
+    /// </summary>
+    public MailSortOrder SortOrder { get; init; } = MailSortOrder.NewestFirst;
+
+    // ── Text filters ───────────────────────────────────────────────────────────
+
+    /// <summary>
+    /// Case-insensitive substring the message subject must contain.
+    /// Maps to IMAP <c>SUBJECT</c>.
+    /// </summary>
+    public string? SubjectContains { get; init; } = null;
+
+    /// <summary>
+    /// Case-insensitive substring that must appear in the <c>From</c> header.
+    /// Maps to IMAP <c>FROM</c>.
+    /// </summary>
+    public string? SenderContains { get; init; } = null;
+
+    /// <summary>
+    /// Case-insensitive substring that must appear in <c>To</c> or <c>Cc</c>.
+    /// Maps to IMAP <c>TO</c>.
+    /// </summary>
+    public string? RecipientContains { get; init; } = null;
+
+    /// <summary>
+    /// Case-insensitive substring that must appear anywhere in the message body (text or HTML part).
+    /// Maps to IMAP <c>BODY</c>.
+    /// </summary>
+    public string? BodyContains { get; init; } = null;
+
+    // ── Structured filters ─────────────────────────────────────────────────────
+
+    /// <summary>
+    /// Constrains results to a specific UID or a UID range.
+    /// See <see cref="UidFilter"/> for mutual-exclusion rules between its fields.
+    /// </summary>
+    public UidFilter? Uid { get; init; } = null;
+
+    /// <summary>
+    /// Constrains results to messages received within a date range.
+    /// See <see cref="DateFilter"/> for rules between its fields.
+    /// </summary>
+    public DateFilter? Date { get; init; } = null;
+}
+#endif

src/core/DigitalData.MessagingService.Application/Common/Dto/MailSearch/MailSortOrder.cs

@@ -0,0 +1,17 @@
+namespace DigitalData.MessagingService.Application.Common.Dto.MailSearch;
+
+/// <summary>
+/// Controls the order in which fetched messages are returned.
+/// </summary>
+public enum MailSortOrder
+{
+    /// <summary>
+    /// Newest messages first (default).
+    /// </summary>
+    NewestFirst,
+
+    /// <summary>
+    /// Oldest messages first.
+    /// </summary>
+    OldestFirst
+}

src/core/DigitalData.MessagingService.Application/Common/Dto/MailSearch/UidFilter.cs

@@ -0,0 +1,16 @@
+#if NET
+namespace DigitalData.MessagingService.Application.Common.Dto.MailSearch;
+
+/// <summary>
+/// Constrains the search to a specific UID or a UID range.
+/// </summary>
+/// <remarks>
+/// Use <see cref="Absolute"/> for an exact single-message lookup.
+/// Use <see cref="Min"/> and/or <see cref="Max"/> for an open or closed range.
+/// Mixing <see cref="Absolute"/> with <see cref="Min"/> or <see cref="Max"/> is not allowed.
+/// </remarks>
+/// <param name="Min">Lower bound of the UID range (inclusive). Ignored when <see cref="Absolute"/> is set.</param>
+/// <param name="Max">Upper bound of the UID range (inclusive). Ignored when <see cref="Absolute"/> is set.</param>
+/// <param name="Absolute">Exact UID to match. When set, <see cref="Min"/> and <see cref="Max"/> must be <see langword="null"/>.</param>
+public record UidFilter(long? Min = null, long? Max = null, long? Absolute = null);
+#endif

src/core/DigitalData.MessagingService.Application/Common/Dto/ReceivedEmailDto.cs

@@ -0,0 +1,112 @@
+namespace DigitalData.MessagingService.Application.Common.Dto;
+
+/// <summary>
+/// Represents an email message received via IMAP.
+/// </summary>
+public sealed record ReceivedEmailDto
+{
+    /// <summary>
+    /// Unique identifier of the message on the IMAP server (UID).
+    /// </summary>
+#if NET
+    public long Uid { get; init; }
+#else
+    public long Uid { get; set; }
+#endif
+
+    /// <summary>
+    /// ID of the email account this message belongs to.
+    /// </summary>
+#if NET
+    public int AccountId { get; init; }
+#else
+    public int AccountId { get; set; }
+#endif
+
+    /// <summary>
+    /// Sender address (From header).
+    /// </summary>
+#if NET
+    public string From { get; init; } = string.Empty;
+#else
+    public string From { get; set; } = string.Empty;
+#endif
+
+    /// <summary>
+    /// Recipient addresses (To header).
+    /// </summary>
+#if NET
+    public IEnumerable<string> To { get; init; } = [];
+#else
+    public IEnumerable<string> To { get; set; } = [];
+#endif
+
+    /// <summary>
+    /// CC addresses.
+    /// </summary>
+#if NET
+    public IEnumerable<string> Cc { get; init; } = [];
+#else
+    public IEnumerable<string> Cc { get; set; } = [];
+#endif
+
+    /// <summary>
+    /// Email subject.
+    /// </summary>
+#if NET
+    public string Subject { get; init; } = string.Empty;
+#else
+    public string Subject { get; set; } = string.Empty;
+#endif
+
+    /// <summary>
+    /// Plain-text body (may be empty when only HTML is present).
+    /// </summary>
+#if NET
+    public string TextBody { get; init; } = string.Empty;
+#else
+    public string TextBody { get; set; } = string.Empty;
+#endif
+
+    /// <summary>
+    /// HTML body (may be empty when only plain-text is present).
+    /// </summary>
+#if NET
+    public string HtmlBody { get; init; } = string.Empty;
+#else
+    public string HtmlBody { get; set; } = string.Empty;
+#endif
+
+    /// <summary>
+    /// Date/time the message was sent (Date header).
+    /// </summary>
+#if NET
+    public DateTime Date { get; init; }
+#else
+    public DateTime Date { get; set; }
+#endif
+
+    /// <summary>
+    /// Attachments included with this message.
+    /// </summary>
+#if NET
+    public IEnumerable<EmailAttachmentDto> Attachments { get; init; } = [];
+#else
+    public IEnumerable<EmailAttachmentDto> Attachments { get; set; } = [];
+#endif
+
+    /// <summary>
+    /// Whether the message has been marked as seen/read on the server.
+    /// </summary>
+#if NET
+    public bool IsSeen { get; init; }
+#else
+    public bool IsSeen { get; set; }
+#endif
+
+#if NET
+    public required string Folder { get; init; }
+#else
+    public string Folder { get; set; } = null!;
+#endif
+}

src/core/DigitalData.MessagingService.Application/Common/Dto/SendingEmailCreateDto.cs

@@ -1,11 +1,7 @@
-using System;
+namespace DigitalData.MessagingService.Application.Common.Dto;
 
-namespace DigitalData.MessagingService.Publisher.Abstraction;
-
-public class OutgoingEmailEvent
+public record SendingEmailCreateDto
 {
-    public Guid Id { get; set; }
-
     /// <summary>
     /// Recipient email address
     /// </summary>

src/core/DigitalData.MessagingService.Application/Common/Dto/SendingEmailEvent.cs

@@ -0,0 +1,22 @@
+namespace DigitalData.MessagingService.Application.Common.Dto;
+
+public record SendingEmailEvent
+{
+#if NETFRAMEWORK
+    public Guid Id { get; set; }
+#else
+    public required Guid Id { get; init; }
+#endif
+
+#if NETFRAMEWORK
+    public EmailContext Mail { get; set; } = null!;
+#else
+    public required EmailContext Mail { get; init; }
+#endif
+
+#if NETFRAMEWORK
+    public DateTime QueuedAt { get; set; }
+#else
+    public required DateTime QueuedAt { get; init; }
+#endif
+}

src/core/DigitalData.MessagingService.Application/Common/Dtos/EmailAccountDto.cs

@@ -1,21 +0,0 @@
-namespace DigitalData.MessagingService.Application.Common.Dtos;
-
-/// <summary>
-/// DTO for EmailAccount query results.
-/// </summary>
-public class EmailAccountDto
-{
-    public string Username { get; set; } = null!;
-
-    public string Password { get; set; } = null!;
-
-    public bool PasswordEncrypted { get; set; } = false;
-
-    public string SmtpServer { get; set; } = null!;
-
-    public int SmtpPort { get; set; }
-
-    public bool SmtpUseSsl { get; set; }
-
-    public bool UseOAuth2 { get; set; }
-}

src/core/DigitalData.MessagingService.Application/Common/Interfaces/IEmailService.cs

@@ -1,3 +1,5 @@
+using DigitalData.MessagingService.Application.Common.Dto;
+
 namespace DigitalData.MessagingService.Application.Common.Interfaces;
 
 /// <summary>
@@ -12,5 +14,5 @@ public interface IEmailService
     /// Sends an email using the configured SMTP account.
     /// SMTP credentials are configured in appsettings.json (EmailAccount section).
     /// </summary>
-    Task SendEmailAsync(string to, string subject, string body, bool isHtml = true, CancellationToken cancellationToken = default);
+    Task SendEmailAsync(EmailContext context, CancellationToken cancellationToken = default);
 }

src/core/DigitalData.MessagingService.Application/Common/Interfaces/IImapEmailService.cs

@@ -0,0 +1,41 @@
+#if NET
+using DigitalData.MessagingService.Application.Common.Dto;
+using DigitalData.MessagingService.Domain.Entities;
+
+namespace DigitalData.MessagingService.Application.Common.Interfaces;
+
+/// <summary>
+/// Service interface for reading emails via IMAP.
+/// </summary>
+public interface IImapEmailService
+{
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <param name="account"></param>
+    /// <param name="folder"></param>
+    /// <param name="cancel"></param>
+    /// <returns></returns>
+    Task<EmailSyncResult> SyncEmailsAsync(
+            EmailAccount account,
+            string folder = "INBOX",
+            CancellationToken cancel = default);
+
+    /// <summary>
+    /// Marks a message as seen (read) on the server.
+    /// </summary>
+    Task MarkAsSeenAsync(
+        EmailAccount account,
+        long uid,
+        string folder = "INBOX",
+        CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Gets the last IMAP sync date for the specified account and folder.
+    /// </summary>
+    /// <param name="accountId"></param>
+    /// <param name="folder"></param>
+    /// <returns></returns>
+    DateTime? GetLastImapSyncDate(int accountId, string folder = "INBOX");
+}
+#endif

src/core/DigitalData.MessagingService.Application/Common/Interfaces/ISendingEmailPublisher.cs

@@ -0,0 +1,13 @@
+using DigitalData.MessagingService.Application.Common.Dto;
+
+namespace DigitalData.MessagingService.Application.Common.Interfaces;
+
+/// <summary>
+/// Email queue interface for outgoing emails.
+/// </summary>
+public interface ISendingEmailPublisher
+{
+    Task EnqueueAsync(SendingEmailEvent sendingEmailEvent, CancellationToken cancellationToken = default);
+
+    Task<int> GetQueueDepthAsync(CancellationToken cancellationToken = default);
+}

src/core/DigitalData.MessagingService.Application/Common/Interfaces/Repositories/IReceivedEmailRepository.cs

@@ -0,0 +1,11 @@
+#if NET
+using DigitalData.MessagingService.Application.Common.Dto.MailSearch;
+using DigitalData.MessagingService.Domain.Entities;
+
+namespace DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
+
+public interface IReceivedEmailRepository : IRepository<ReceivedEmail>
+{
+    public Task<IEnumerable<ReceivedEmail>> FindAsync(MailSearchFilter mailSearchFilter, EmailAccount? accountQuery = null, CancellationToken cancellationToken = default);
+}
+#endif

src/core/DigitalData.MessagingService.Application/Common/Interfaces/Repositories/IRepository.cs

@@ -1,6 +1,6 @@
 using System.Linq.Expressions;
 
-namespace DigitalData.MessagingService.Application.Common.Interfaces;
+namespace DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
 
 /// <summary>
 /// Generic repository interface for CRUD operations.
@@ -11,6 +11,8 @@ public interface IRepository<TEntity> where TEntity : class
     // CREATE
     Task<TEntity> CreateAsync<TDto>(TDto dto, CancellationToken cancellationToken = default);
 
+    Task<IEnumerable<TEntity>> CreateRangeAsync<TDto>(IEnumerable<TDto> dtos, CancellationToken cancellationToken = default);
+
     // READ
     Task<TEntity?> GetByIdAsync(int id, CancellationToken cancellationToken = default);
     Task<IEnumerable<TEntity>> GetAllAsync(CancellationToken cancellationToken = default);
@@ -20,6 +22,11 @@ public interface IRepository<TEntity> where TEntity : class
     Task<int> CountAsync(Expression<Func<TEntity, bool>>? predicate = null, CancellationToken cancellationToken = default);
     Task<bool> AnyAsync(Expression<Func<TEntity, bool>> predicate, CancellationToken cancellationToken = default);
 
+    // UPSERT
+    Task<(TEntity Entity, bool Created)> UpsertAsync<TDto>(Expression<Func<TEntity, bool>> predicate, TDto dto, CancellationToken cancellationToken = default);
+    
+    Task<(TEntity Entity, bool Created)> UpsertSingleAsync<TDto>(Expression<Func<TEntity, bool>> predicate, TDto dto, CancellationToken cancellationToken = default);
+
     // UPDATE
     Task UpdateSingleAsync<TDto>(Expression<Func<TEntity, bool>> predicate, TDto dto, CancellationToken cancellationToken = default);
     Task<int> UpdateAsync<TDto>(Expression<Func<TEntity, bool>> predicate, TDto dto, CancellationToken cancellationToken = default);

src/core/DigitalData.MessagingService.Application/Common/Mappings/EmailMappingProfile.cs

@@ -1,6 +1,9 @@
+#if NET
 using AutoMapper;
 using DigitalData.MessagingService.Application.EmailSending.Commands;
-using DigitalData.MessagingService.Publisher.Abstraction;
+using DigitalData.MessagingService.Application.Common.Dto;
+using DigitalData.MessagingService.Domain.Entities;
+using DigitalData.MessagingService.Application.Common.Dto.EmailAccounts;
 
 namespace DigitalData.MessagingService.Application.Common.Mappings;
 
@@ -11,9 +14,28 @@ public class EmailMappingProfile : Profile
 {
     public EmailMappingProfile()
     {
-        // SendEmailCommand -> OutgoingEmailEvent
-        CreateMap<SendEmailCommand, OutgoingEmailEvent>()
-            .ForMember(dest => dest.Id, opt => opt.MapFrom(_ => Guid.NewGuid()))
-            .ForMember(dest => dest.QueuedAt, opt => opt.MapFrom(_ => DateTime.Now));
+        // PublishEmailCommand -> Email
+        // Sender is resolved via MediatR in the handler and set separately after mapping.
+        CreateMap<PublishEmailCommand, EmailContext>()
+            .ForMember(dest => dest.Sender, opt => opt.Ignore())
+            .ForMember(dest => dest.Attachments, opt => opt.MapFrom(src => src.Attachments));
+
+        // EmailAccountDto -> EmailAccount
+        CreateMap<EmailAccount, EmailAccountDto>();
+        CreateMap<EmailAccountModificationDto, EmailAccount>();
+
+        // ReceivedEmailDto <-> ReceivedEmail
+        CreateMap<ReceivedEmailDto, ReceivedEmail>()
+            .ForMember(dest => dest.Id, opt => opt.Ignore())
+            .ForMember(dest => dest.Account, opt => opt.Ignore());
+        CreateMap<ReceivedEmail, ReceivedEmailDto>();
+
+        // EmailAttachmentDto <-> EmailAttachment
+        CreateMap<EmailAttachmentDto, EmailAttachment>()
+            .ForMember(dest => dest.Id, opt => opt.Ignore())
+            .ForMember(dest => dest.EmailId, opt => opt.Ignore())
+            .ForMember(dest => dest.Email, opt => opt.Ignore());
+        CreateMap<EmailAttachment, EmailAttachmentDto>();
     }
 }
+#endif

src/core/DigitalData.MessagingService.Application/Common/Options/EmailAccountsOptions.cs

@@ -0,0 +1,28 @@
+#if NET
+using DigitalData.MessagingService.Application.Common.Dto;
+using DigitalData.MessagingService.Application.Common.Dto.EmailAccounts;
+using DigitalData.MessagingService.Application.EmailAccounts.Commands;
+using DigitalData.MessagingService.Domain.Entities;
+
+namespace DigitalData.MessagingService.Application.Common.Options;
+
+/// <summary>
+/// Wrapper options class that holds a list of <see cref="Dto.EmailAccount"/> entries
+/// bound from the <c>EmailAccounts</c> configuration section.
+/// </summary>
+public class EmailAccountsOptions
+{
+    public const string SectionName = "EmailAccounts";
+
+    /// <summary>
+    /// The list of configured email accounts.
+    /// </summary>
+    public required IEnumerable<EmailAccountModificationDto> Accounts { get; init; } = [];
+
+    /// <summary>
+    /// How often the IMAP sync worker polls for new emails, in seconds.
+    /// Defaults to 300 seconds (5 minutes).
+    /// </summary>
+    public int SyncIntervalSeconds { get; init; } = 300;
+}
+#endif

src/core/DigitalData.MessagingService.Application/Common/ValueObjects/Modification.cs

@@ -0,0 +1,6 @@
+namespace DigitalData.MessagingService.Application.Common.ValueObjects;
+
+public enum Modification
+{
+    Upsert
+}

src/core/DigitalData.MessagingService.Application/DependencyInjection.cs

@@ -1,7 +1,9 @@
-using System.Reflection;
+#if NET
+using DigitalData.MessagingService.Application.Common.Options;
 using FluentValidation;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
+using System.Reflection;
 
 namespace DigitalData.MessagingService.Application;
 
@@ -35,6 +37,10 @@ public static class DependencyInjection
         // FluentValidation - Register all validators
         services.AddValidatorsFromAssembly(assembly);
 
+        // Register EmailAccounts configuration (IOptions<EmailAccountsOptions>)
+        services.Configure<EmailAccountsOptions>(configuration.GetSection(EmailAccountsOptions.SectionName));
+
         return services;
     }
 }
+#endif

src/core/DigitalData.MessagingService.Application/DigitalData.MessagingService.Application.csproj

@@ -1,26 +1,23 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
-    <ImplicitUsings>enable</ImplicitUsings>
-    <Nullable>enable</Nullable>
+	  <TargetFrameworks>net462;net480;net8.0</TargetFrameworks>
+	  <ImplicitUsings>enable</ImplicitUsings>
+	  <Nullable>enable</Nullable>
+	  <LangVersion>latest</LangVersion>
   </PropertyGroup>
 
   <ItemGroup>
     <ProjectReference Include="..\DigitalData.MessagingService.Domain\DigitalData.MessagingService.Domain.csproj" />
-    <ProjectReference Include="..\DigitalData.MessagingService.Publisher.Abstraction\DigitalData.MessagingService.Publisher.Abstraction.csproj" />
   </ItemGroup>
 
-  <ItemGroup>
+  <ItemGroup Condition="'$(TargetFramework)' == 'net8.0'">
     <PackageReference Include="AutoMapper" Version="16.2.0" />
     <PackageReference Include="FluentValidation.DependencyInjectionExtensions" Version="12.1.1" />
     <PackageReference Include="MediatR" Version="14.2.0" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Abstractions" Version="10.0.10" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Binder" Version="10.0.10" />
-  </ItemGroup>
-
-  <ItemGroup>
-    <Folder Include="Common\Dtos\" />
+    <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="8.0.0" />
   </ItemGroup>
 
 </Project>

src/core/DigitalData.MessagingService.Application/EmailAccounts/Commands/EmailAccountModificationCommand.cs

@@ -0,0 +1,36 @@
+#if NET
+using DigitalData.MessagingService.Application.Common.Dto.EmailAccounts;
+using DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
+using DigitalData.MessagingService.Application.Common.ValueObjects;
+using DigitalData.MessagingService.Domain.Entities;
+using MediatR;
+using System.Security.Principal;
+
+namespace DigitalData.MessagingService.Application.EmailAccounts.Commands;
+
+/// <summary>
+/// DTO for a single email account configuration.
+/// </summary>
+public record EmailAccountModificationCommand : IRequest<(EmailAccount, bool)>
+{
+    public required EmailAccountModificationDto ModifiedAccount { get; init; }
+
+    public required Modification Modification { get; init; }
+}
+
+/// <summary>
+/// 
+/// </summary>
+/// <param name="Repo"></param>
+public class EmailAccountModificationCommandHandler(IRepository<EmailAccount> Repo) : IRequestHandler<EmailAccountModificationCommand, (EmailAccount, bool)>
+{
+    public async Task<(EmailAccount, bool)> Handle(EmailAccountModificationCommand request, CancellationToken cancellationToken)
+    {
+        return request.Modification switch
+        {
+            Modification.Upsert => await Repo.UpsertAsync(a => a.Username == request.ModifiedAccount.Username, request.ModifiedAccount, cancellationToken),
+            _ => throw new NotSupportedException($"Modification type '{request.Modification}' is not supported in email account modification."),
+        };
+    }
+}
+#endif

src/core/DigitalData.MessagingService.Application/EmailAccounts/Queries/GetEmailAccountQuery.cs

@@ -0,0 +1,37 @@
+#if NET
+using MediatR;
+using DigitalData.MessagingService.Domain.Entities;
+using DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
+using AutoMapper;
+using DigitalData.MessagingService.Domain.Exceptions;
+using DigitalData.MessagingService.Application.Common.Dto.EmailAccounts;
+
+namespace DigitalData.MessagingService.Application.EmailAccounts.Queries;
+
+public record GetEmailAccountQuery : IRequest<IEnumerable<EmailAccountDto>>
+{
+    public int? Id { get; init; }
+
+    public string? Username { get; init; }
+}
+
+/// <summary>
+/// Handles queries for retrieving email accounts.
+/// </summary>
+/// <param name="Repo"></param>
+/// <param name="Mapper"></param>
+public class GetEmailAccountQueryHandler(IRepository<EmailAccount> Repo, IMapper Mapper) : IRequestHandler<GetEmailAccountQuery, IEnumerable<EmailAccountDto>>
+{
+    public async Task<IEnumerable<EmailAccountDto>> Handle(GetEmailAccountQuery request, CancellationToken cancellationToken)
+    {
+        var accounts = request.Id is null && request.Username is null 
+            ? await Repo.GetAllAsync(cancellationToken) 
+            : await Repo.FindAsync(request.Id is int id ? x => x.Id == id : x => x.Username == request.Username, cancellationToken: cancellationToken);
+
+        if (accounts.Any())
+            return Mapper.Map<IEnumerable<EmailAccountDto>>(accounts);
+        else
+            throw new NotFoundException($"No email account found for the given criteria ({(request.Id is not null ? $"Id: {request.Id}" : $"Username: {request.Username}")}).");
+    }
+}
+#endif

src/core/DigitalData.MessagingService.Application/EmailAccounts/Validators/GetSenderQueryValidator.cs

@@ -0,0 +1,25 @@
+#if NET
+using DigitalData.MessagingService.Application.EmailAccounts.Queries;
+using FluentValidation;
+
+namespace DigitalData.MessagingService.Application.EmailAccounts.Validators;
+
+/// <summary>
+/// Validator for <see cref="GetEmailAccountQuery"/>.
+/// Either <see cref="GetEmailAccountQuery.Id"/> or <see cref="GetEmailAccountQuery.Username"/> must be provided, but not both.
+/// </summary>
+public class GetSenderQueryValidator : AbstractValidator<GetEmailAccountQuery>
+{
+    public GetSenderQueryValidator()
+    {
+        When(x => x.Username is not null, () =>
+        {
+            RuleFor(x => x.Username)
+                .NotEmpty()
+                .WithMessage("Username must not be empty.")
+                .MaximumLength(200)
+                .WithMessage("Username must not exceed 200 characters.");
+        });
+    }
+}
+#endif

src/core/DigitalData.MessagingService.Application/EmailReceiving/Commands/MarkEmailAsSeenCommand.cs

@@ -0,0 +1,48 @@
+#if NET
+using DigitalData.MessagingService.Application.Common.Interfaces;
+using DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
+using DigitalData.MessagingService.Application.EmailAccounts.Queries;
+using DigitalData.MessagingService.Domain.Entities;
+using DigitalData.MessagingService.Domain.Exceptions;
+using MediatR;
+using Microsoft.Extensions.Logging;
+
+namespace DigitalData.MessagingService.Application.EmailReceiving.Commands;
+
+/// <summary>
+/// Command to mark a single IMAP message as seen (read).
+/// </summary>
+public record MarkEmailAsSeenCommand : IRequest
+{
+    public required GetEmailAccountQuery Account { get; init; }
+
+    /// <summary>
+    /// UID of the message to mark as seen.
+    /// </summary>
+    public required long Uid { get; init; }
+
+    /// <summary>
+    /// Mailbox folder the message resides in (default: "INBOX").
+    /// </summary>
+    public string Folder { get; init; } = "INBOX";
+}
+
+public class MarkEmailAsSeenCommandHandler(IImapEmailService ImapService, ILogger<MarkEmailAsSeenCommandHandler> Logger, IRepository<EmailAccount> Repo) : IRequestHandler<MarkEmailAsSeenCommand>
+{
+    public async Task Handle(MarkEmailAsSeenCommand request, CancellationToken cancellationToken)
+    {
+        var accounts = await Repo.FindAsync(request.Account.Id is int id ? x => x.Id == id : x => x.Username == request.Account.Username, cancellationToken: cancellationToken);
+
+        if (accounts.Count() > 1)
+            Logger.LogWarning("Multiple email accounts found for the given criteria ({Criteria}). Returning the first one.", request.Account.Id is not null ? $"Id: {request.Account.Id}" : $"Username: {request.Account.Username}");
+
+        var account = accounts.FirstOrDefault()
+            ?? throw new NotFoundException($"No email account found for the given criteria (Id: {request.Account.Id}, Username: {request.Account.Username}).");
+
+        if (string.IsNullOrWhiteSpace(account.ImapServer))
+            throw new BadRequestException($"IMAP is not configured for account '{account.Username}' (Id: {account.Id}). Set ImapServer in EmailAccounts configuration.");
+
+        await ImapService.MarkAsSeenAsync(account, request.Uid, request.Folder, cancellationToken);
+    }
+}
+#endif

src/core/DigitalData.MessagingService.Application/EmailReceiving/Queries/ReadEmailQuery.cs

@@ -0,0 +1,51 @@
+#if NET
+using AutoMapper;
+using DigitalData.MessagingService.Application.Common.Dto;
+using DigitalData.MessagingService.Application.Common.Dto.MailSearch;
+using DigitalData.MessagingService.Application.Common.Interfaces;
+using DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
+using DigitalData.MessagingService.Application.EmailAccounts.Queries;
+using DigitalData.MessagingService.Domain.Entities;
+using DigitalData.MessagingService.Domain.Exceptions;
+using MediatR;
+using Microsoft.Extensions.Logging;
+
+namespace DigitalData.MessagingService.Application.EmailReceiving.Queries;
+
+/// <summary>
+/// Query to fetch emails from an IMAP mailbox.
+/// </summary>
+public record ReadEmailQuery : IRequest<IEnumerable<ReceivedEmailDto>>
+{
+    /// <summary>
+    /// Identifies the email account to use.
+    /// </summary>
+    public required GetEmailAccountQuery Account { get; init; }
+
+    /// <summary>
+    /// Mail query used to filter and limit the emails retrieved.
+    /// </summary>
+    public MailSearchFilter Mail { get; init; } = new();
+}
+
+public class ReadEmailQueryHandler(IMapper Mapper, ILogger<ReadEmailQueryHandler> Logger, IRepository<EmailAccount> EmailAccountRepo, IReceivedEmailRepository MailRepo) : IRequestHandler<ReadEmailQuery, IEnumerable<ReceivedEmailDto>>
+{
+    public async Task<IEnumerable<ReceivedEmailDto>> Handle(ReadEmailQuery request, CancellationToken cancellationToken)
+    {
+        var accounts = await EmailAccountRepo.FindAsync(request.Account.Id is int id ? x => x.Id == id : x => x.Username == request.Account.Username, cancellationToken: cancellationToken);
+
+        if (accounts.Count() > 1)
+            Logger.LogWarning("Multiple email accounts found for the given criteria ({Criteria}). Returning the first one.", request.Account.Id is not null ? $"Id: {request.Account.Id}" : $"Username: {request.Account.Username}");
+
+        var account = accounts.FirstOrDefault()
+            ?? throw new NotFoundException($"No email account found for the given criteria (Id: {request.Account.Id}, Username: {request.Account.Username}).");
+
+        if (string.IsNullOrWhiteSpace(account.ImapServer))
+            throw new BadRequestException(
+                $"IMAP is not configured for account '{account.Username}' (Id: {account.Id}). Set ImapServer in EmailAccounts configuration.");
+
+        var mails = await MailRepo.FindAsync(request.Mail, account, cancellationToken);
+        return Mapper.Map<IEnumerable<ReceivedEmailDto>>(mails);
+    }
+}
+#endif

src/core/DigitalData.MessagingService.Application/EmailReceiving/Validators/DateFilterValidator.cs

@@ -0,0 +1,39 @@
+#if NET
+using DigitalData.MessagingService.Application.Common.Dto.MailSearch;
+using FluentValidation;
+
+namespace DigitalData.MessagingService.Application.EmailReceiving.Validators;
+
+/// <summary>
+/// Validates a <see cref="DateFilter"/> value object.
+/// </summary>
+public class DateFilterValidator : AbstractValidator<DateFilter>
+{
+    public DateFilterValidator()
+    {
+        // At least one field must be provided
+        RuleFor(x => x)
+            .Must(d => d.After is not null || d.Before is not null)
+            .WithName("Date")
+            .WithMessage("DateFilter must specify at least one of: After or Before.");
+
+        // Dates must not be in the future
+        RuleFor(x => x.After)
+            .LessThanOrEqualTo(DateTime.UtcNow)
+            .WithMessage("Date.After must not be in the future.")
+            .When(x => x.After is not null);
+
+        RuleFor(x => x.Before)
+            .LessThanOrEqualTo(DateTime.UtcNow)
+            .WithMessage("Date.Before must not be in the future.")
+            .When(x => x.Before is not null);
+
+        // Range coherence: After must be earlier than Before
+        RuleFor(x => x)
+            .Must(d => d.After!.Value < d.Before!.Value)
+            .WithName("Date.Range")
+            .WithMessage("Date.After must be earlier than Date.Before.")
+            .When(x => x.After is not null && x.Before is not null);
+    }
+}
+#endif

src/core/DigitalData.MessagingService.Application/EmailReceiving/Validators/FetchEmailsQueryValidator.cs

@@ -0,0 +1,24 @@
+#if NET
+using DigitalData.MessagingService.Application.EmailReceiving.Queries;
+using FluentValidation;
+
+namespace DigitalData.MessagingService.Application.EmailReceiving.Validators;
+
+/// <summary>
+/// Validates a <see cref="ReadEmailQuery"/> before it is handled by <see cref="ReadEmailQueryHandler"/>.
+/// </summary>
+public class FetchEmailsQueryValidator : AbstractValidator<ReadEmailQuery>
+{
+    public FetchEmailsQueryValidator()
+    {
+        RuleFor(x => x.Account)
+            .NotNull()
+            .WithMessage("Account query must not be null.");
+
+        RuleFor(x => x.Mail)
+            .NotNull()
+            .WithMessage("Mail search filter must not be null.")
+            .SetValidator(new MailSearchFilterValidator());
+    }
+}
+#endif

src/core/DigitalData.MessagingService.Application/EmailReceiving/Validators/MailSearchFilterValidator.cs

@@ -0,0 +1,53 @@
+#if NET
+using DigitalData.MessagingService.Application.Common.Dto.MailSearch;
+using FluentValidation;
+
+namespace DigitalData.MessagingService.Application.EmailReceiving.Validators;
+
+/// <summary>
+/// Validates a <see cref="MailSearchFilter"/> instance before it is dispatched to the IMAP service.
+/// </summary>
+public class MailSearchFilterValidator : AbstractValidator<MailSearchFilter>
+{
+    public MailSearchFilterValidator()
+    {
+        RuleFor(x => x.Folder)
+            .NotEmpty()
+            .WithMessage("Folder must not be empty.")
+            .MaximumLength(255)
+            .WithMessage("Folder name must not exceed 255 characters.");
+
+        RuleFor(x => x.MaxCount)
+            .GreaterThanOrEqualTo(0)
+            .WithMessage("MaxCount must be 0 (unlimited) or a positive number.");
+
+        RuleFor(x => x.SubjectContains)
+            .MaximumLength(500)
+            .WithMessage("SubjectContains must not exceed 500 characters.")
+            .When(x => x.SubjectContains is not null);
+
+        RuleFor(x => x.SenderContains)
+            .MaximumLength(320)
+            .WithMessage("SenderContains must not exceed 320 characters.")
+            .When(x => x.SenderContains is not null);
+
+        RuleFor(x => x.RecipientContains)
+            .MaximumLength(320)
+            .WithMessage("RecipientContains must not exceed 320 characters.")
+            .When(x => x.RecipientContains is not null);
+
+        RuleFor(x => x.BodyContains)
+            .MaximumLength(1000)
+            .WithMessage("BodyContains must not exceed 1000 characters.")
+            .When(x => x.BodyContains is not null);
+
+        RuleFor(x => x.Uid)
+            .SetValidator(new UidFilterValidator()!)
+            .When(x => x.Uid is not null);
+
+        RuleFor(x => x.Date)
+            .SetValidator(new DateFilterValidator()!)
+            .When(x => x.Date is not null);
+    }
+}
+#endif

src/core/DigitalData.MessagingService.Application/EmailReceiving/Validators/UidFilterValidator.cs

@@ -0,0 +1,50 @@
+#if NET
+using DigitalData.MessagingService.Application.Common.Dto.MailSearch;
+using FluentValidation;
+
+namespace DigitalData.MessagingService.Application.EmailReceiving.Validators;
+
+/// <summary>
+/// Validates a <see cref="UidFilter"/> value object.
+/// </summary>
+public class UidFilterValidator : AbstractValidator<UidFilter>
+{
+    public UidFilterValidator()
+    {
+        // Absolute and range are mutually exclusive
+        RuleFor(x => x)
+            .Must(u => u.Absolute is null || (u.Min is null && u.Max is null))
+            .WithName("Uid.Absolute")
+            .WithMessage("Uid.Absolute cannot be combined with Uid.Min or Uid.Max. Use either an exact UID or a range.");
+
+        // At least one field must be provided
+        RuleFor(x => x)
+            .Must(u => u.Absolute is not null || u.Min is not null || u.Max is not null)
+            .WithName("Uid")
+            .WithMessage("UidFilter must specify at least one of: Absolute, Min, or Max.");
+
+        // All UID values must be positive
+        RuleFor(x => x.Absolute)
+            .GreaterThan(0)
+            .WithMessage("Uid.Absolute must be a positive number.")
+            .When(x => x.Absolute is not null);
+
+        RuleFor(x => x.Min)
+            .GreaterThan(0)
+            .WithMessage("Uid.Min must be a positive number.")
+            .When(x => x.Min is not null);
+
+        RuleFor(x => x.Max)
+            .GreaterThan(0)
+            .WithMessage("Uid.Max must be a positive number.")
+            .When(x => x.Max is not null);
+
+        // Range coherence: Min must be less than or equal to Max
+        RuleFor(x => x)
+            .Must(u => u.Min!.Value <= u.Max!.Value)
+            .WithName("Uid.Range")
+            .WithMessage("Uid.Min must be less than or equal to Uid.Max.")
+            .When(x => x.Min is not null && x.Max is not null);
+    }
+}
+#endif

src/core/DigitalData.MessagingService.Application/EmailSending/Commands/PublishEmailCommand.cs

@@ -0,0 +1,82 @@
+#if NET
+using AutoMapper;
+using DigitalData.MessagingService.Application.Common.Dto;
+using DigitalData.MessagingService.Application.Common.Interfaces;
+using DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
+using DigitalData.MessagingService.Application.EmailAccounts.Queries;
+using DigitalData.MessagingService.Domain.Entities;
+using DigitalData.MessagingService.Domain.Exceptions;
+using MediatR;
+using Microsoft.Extensions.Logging;
+using System.Text.Json.Serialization;
+
+namespace DigitalData.MessagingService.Application.EmailSending.Commands;
+
+/// <summary>
+/// Command to send an email (enqueue to RabbitMQ)
+/// </summary>
+public record PublishEmailCommand : IRequest<Guid>
+{
+    public required GetEmailAccountQuery Sender { get; init; }
+
+    /// <summary>
+    /// Recipient email addresses
+    /// </summary>
+    public required IEnumerable<string> Recipients { get; init; }
+
+    /// <summary>
+    /// Email subject
+    /// </summary>
+    public required string Subject { get; init; }
+
+    /// <summary>
+    /// Email body (HTML or plain text)
+    /// </summary>
+    public required string Body { get; init; }
+
+    /// <summary>
+    /// Is HTML email (default: true)
+    /// </summary>
+    public bool IsHtml { get; init; } = true;
+
+    [JsonIgnore]
+    internal IEnumerable<EmailAttachmentDto> Attachments { get; private init; } = [];
+
+    /// <summary>
+    /// Returns a new command instance with the supplied attachments.
+    /// Called by the controller after resolving uploaded files.
+    /// </summary>
+    public PublishEmailCommand WithAttachments(IEnumerable<EmailAttachmentDto> attachments)
+        => this with { Attachments = attachments };
+}
+
+/// <summary>
+/// Handler for PublishEmailCommand
+/// Resolves the sender account via MediatR, maps to SendingEmailEvent and enqueues to RabbitMQ
+/// </summary>
+public class PublishEmailCommandHandler(IRepository<EmailAccount> Repo, ISendingEmailPublisher Publisher, IMapper Mapper, ILogger<PublishEmailCommandHandler> Logger) : IRequestHandler<PublishEmailCommand, Guid>
+{
+    public async Task<Guid> Handle(PublishEmailCommand request, CancellationToken cancellationToken)
+    {
+        var senderAccounts = await Repo.FindAsync(request.Sender.Id is int id ? x => x.Id == id : x => x.Username == request.Sender.Username, cancellationToken: cancellationToken);
+
+        if (senderAccounts.Count() > 1)
+            Logger.LogWarning("Multiple email accounts found for the given criteria ({Criteria}). Returning the first one.", request.Sender.Id is not null ? $"Id: {request.Sender.Id}" : $"Username: {request.Sender.Username}");
+
+        var senderAccount = senderAccounts.FirstOrDefault()
+            ?? throw new NotFoundException($"No email account found for the given sender criteria (Id: {request.Sender.Id}, Username: {request.Sender.Username}).");
+
+        var email = Mapper.Map<EmailContext>(request) with { Sender = senderAccount };
+
+        // Enqueue to RabbitMQ
+        var sendingEmailEvent = new SendingEmailEvent()
+        {
+            Id = Guid.NewGuid(),
+            Mail = email,
+            QueuedAt = DateTime.Now
+        };
+        await Publisher.EnqueueAsync(sendingEmailEvent, cancellationToken);
+        return sendingEmailEvent.Id;
+    }
+}
+#endif

src/core/DigitalData.MessagingService.Application/EmailSending/Commands/SendEmailCommand.cs

@@ -1,47 +0,0 @@
-using AutoMapper;
-using DigitalData.MessagingService.Publisher.Abstraction;
-using MediatR;
-
-namespace DigitalData.MessagingService.Application.EmailSending.Commands;
-
-/// <summary>
-/// Command to send an email (enqueue to RabbitMQ)
-/// </summary>
-public record SendEmailCommand : IRequest<OutgoingEmailEvent>
-{
-    /// <summary>
-    /// Recipient email address
-    /// </summary>
-    public required string Recipient { get; init; }
-
-    /// <summary>
-    /// Email subject
-    /// </summary>
-    public required string Subject { get; init; }
-
-    /// <summary>
-    /// Email body (HTML or plain text)
-    /// </summary>
-    public required string Body { get; init; }
-
-    /// <summary>
-    /// Is HTML email (default: true)
-    /// </summary>
-    public bool IsHtml { get; init; } = true;
-}
-
-/// <summary>
-/// Handler for SendEmailCommand
-/// Creates EmailOutbox entity via AutoMapper and enqueues to RabbitMQ
-/// </summary>
-public class SendEmailCommandHandler(IOutgoingEmailPublisher Publisher, IMapper Mapper) : IRequestHandler<SendEmailCommand, OutgoingEmailEvent>
-{
-    public async Task<OutgoingEmailEvent> Handle(SendEmailCommand request, CancellationToken cancellationToken)
-    {
-        var outgoingEmailEvent = Mapper.Map<OutgoingEmailEvent>(request);
-
-        // Enqueue to RabbitMQ
-        await Publisher.EnqueueAsync(outgoingEmailEvent, cancellationToken);
-        return outgoingEmailEvent;
-    }
-}

src/core/DigitalData.MessagingService.Application/EmailSending/Validators/SendEmailCommandValidator.cs

@@ -1,22 +1,26 @@
+#if NET
 using DigitalData.MessagingService.Application.EmailSending.Commands;
 using FluentValidation;
 
 namespace DigitalData.MessagingService.Application.EmailSending.Validators;
 
 /// <summary>
-/// Validator for SendEmailCommand
+/// Validator for PublishEmailCommand
 /// </summary>
-public class SendEmailCommandValidator : AbstractValidator<SendEmailCommand>
+public class PublishEmailCommandValidator : AbstractValidator<PublishEmailCommand>
 {
-    public SendEmailCommandValidator()
+    public PublishEmailCommandValidator()
     {
-        RuleFor(x => x.Recipient)
+        RuleFor(x => x.Recipients)
             .NotEmpty()
-            .WithMessage("Recipient is required")
-            .MaximumLength(200)
-            .WithMessage("Recipient must not exceed 200 characters")
-            .EmailAddress()
-            .WithMessage("Recipient must be a valid email address");
+            .WithMessage("Recipients are required")
+            .Must(x => x.Any())
+            .WithMessage("At least one recipient is required")
+            .ForEach(recipient => recipient
+                .NotEmpty()
+                .WithMessage("Recipient email must not be empty")
+                .EmailAddress()
+                .WithMessage("Invalid email address format"));
 
         RuleFor(x => x.Subject)
             .NotEmpty()
@@ -29,3 +33,4 @@ public class SendEmailCommandValidator : AbstractValidator<SendEmailCommand>
             .WithMessage("Body is required");
     }
 }
+#endif

src/core/DigitalData.MessagingService.Domain/DigitalData.MessagingService.Domain.csproj

@@ -11,4 +11,8 @@
     <PackageReference Include="MediatR" Version="12.2.0" />
   </ItemGroup>
 
+  <ItemGroup Condition="'$(TargetFramework)' == 'net462'">
+    <Reference Include="System.ComponentModel.DataAnnotations" />
+  </ItemGroup>
+
 </Project>

src/core/DigitalData.MessagingService.Domain/Entities/EmailAccount.cs

@@ -0,0 +1,75 @@
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace DigitalData.MessagingService.Domain.Entities;
+
+/// <summary>
+/// DTO for a single email account configuration.
+/// </summary>
+[Table("EMAIL_ACCOUNT")]
+public class EmailAccount
+{
+    /// <summary>
+    /// Logical name to identify this account (e.g. "default", "support").
+    /// </summary>
+    [Key]
+    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
+    [Column("ID", TypeName = "int")]
+    public int Id { get; set; }
+
+    [Required]
+    [MaxLength(256)]
+    [Column("USERNAME", TypeName = "nvarchar(256)")]
+#if NET
+    public required string Username { get; set; }
+#else
+    public string Username { get; set; } = null!;
+#endif
+
+    [Required]
+    [MaxLength(512)]
+    [Column("PASSWORD", TypeName = "nvarchar(512)")]
+#if NET
+    public required string Password { get; set; }
+#else
+    public string Password { get; set; } = null!;
+#endif
+
+    [Required]
+    [MaxLength(256)]
+    [Column("SMTP_SERVER", TypeName = "nvarchar(256)")]
+#if NET
+    public required string SmtpServer { get; set; }
+#else
+    public string SmtpServer { get; set; } = null!;
+#endif
+
+    [Column("SMTP_PORT", TypeName = "int")]
+    public int SmtpPort { get; set; }
+
+    [Column("SMTP_USE_SSL", TypeName = "bit")]
+    public bool SmtpUseSsl { get; set; }
+
+    [Column("USE_OAUTH2", TypeName = "bit")]
+    public bool UseOAuth2 { get; set; }
+
+    /// <summary>
+    /// IMAP server hostname (e.g. "imap.example.com").
+    /// Leave empty when this account is send-only.
+    /// </summary>
+    [MaxLength(256)]
+    [Column("IMAP_SERVER", TypeName = "nvarchar(256)")]
+    public string? ImapServer { get; set; }
+
+    /// <summary>
+    /// IMAP server port (993 for SSL, 143 for plain/STARTTLS).
+    /// </summary>
+    [Column("IMAP_PORT", TypeName = "int")]
+    public int ImapPort { get; set; } = 993;
+
+    /// <summary>
+    /// Use SSL/TLS when connecting to the IMAP server.
+    /// </summary>
+    [Column("IMAP_USE_SSL", TypeName = "bit")]
+    public bool ImapUseSsl { get; set; } = true;
+}

src/core/DigitalData.MessagingService.Domain/Entities/EmailAttachment.cs

@@ -0,0 +1,83 @@
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace DigitalData.MessagingService.Domain.Entities;
+
+/// <summary>
+/// Represents a single email attachment.
+/// </summary>
+[Table("EMAIL_ATTACHMENT")]
+public sealed class EmailAttachment
+{
+    [Key]
+    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
+    [Column("ID", TypeName = "bigint")]
+#if NET
+    public long Id { get; init; }
+#else
+    public long Id { get; set; }
+#endif
+
+    /// <summary>
+    /// Display name of the attachment (e.g. "invoice.pdf").
+    /// </summary>
+    [Required]
+    [MaxLength(260)]
+    [Column("FILE_NAME", TypeName = "nvarchar(260)")]
+#if NETFRAMEWORK
+    public string FileName { get; set; } = null!;
+#else
+    public required string FileName { get; init; }
+#endif
+
+    /// <summary>
+    /// Raw content of the attachment.
+    /// </summary>
+    [Required]
+    [Column("CONTENT", TypeName = "varbinary(max)")]
+#if NETFRAMEWORK
+    public byte[] Content { get; set; } = null!;
+#else
+    public required byte[] Content { get; init; }
+#endif
+
+    /// <summary>
+    /// MIME content-type (e.g. "application/pdf", "image/png").
+    /// Defaults to "application/octet-stream" when not specified.
+    /// </summary>
+    [Required]
+    [MaxLength(256)]
+    [Column("CONTENT_TYPE", TypeName = "nvarchar(256)")]
+    public string ContentType { get; set; } = "application/octet-stream";
+
+    /// <summary>
+    /// When <see langword="true"/> the attachment is embedded inline and displayed
+    /// directly inside the email body via a CID reference (e.g. &lt;img src="cid:logo"&gt;).
+    /// When <see langword="false"/> (default) it appears as a regular downloadable attachment.
+    /// </summary>
+    [Column("IS_INLINE", TypeName = "bit")]
+    public bool IsInline { get; set; } = false;
+
+    /// <summary>
+    /// Content-ID used when <see cref="IsInline"/> is <see langword="true"/>.
+    /// Reference it in HTML body as <c>cid:{ContentId}</c>.
+    /// Auto-generated from <see cref="FileName"/> when left empty.
+    /// </summary>
+    [MaxLength(512)]
+    [Column("CONTENT_ID", TypeName = "nvarchar(512)")]
+    public string? ContentId { get; set; }
+
+    [ForeignKey(nameof(Email))]
+    [Column("EMAIL_ID", TypeName = "bigint")]
+#if NET
+    public long EmailId { get; init; }
+#else
+    public long EmailId { get; set; }
+#endif
+
+#if NET
+    public ReceivedEmail? Email { get; init; }
+#else
+    public ReceivedEmail? Email { get; set; }
+#endif
+}

src/core/DigitalData.MessagingService.Domain/Entities/ReceivedEmail.cs

@@ -0,0 +1,142 @@
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace DigitalData.MessagingService.Domain.Entities;
+
+/// <summary>
+/// Represents an email message received via IMAP.
+/// </summary>
+[Table("RECEIVED_EMAIL")]
+public sealed record ReceivedEmail
+{
+    [Key]
+    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
+    [Column("ID", TypeName = "bigint")]
+#if NET
+    public long Id { get; init; }
+#else
+    public long Id { get; set; }
+#endif
+
+    /// <summary>
+    /// Unique identifier of the message on the IMAP server (UID).
+    /// </summary>
+    [Column("UID", TypeName = "bigint")]
+#if NET
+    public long Uid { get; init; }
+#else
+    public long Uid { get; set; }
+#endif
+
+    /// <summary>
+    /// Sender address (From header).
+    /// </summary>
+    [Required]
+    [MaxLength(512)]
+    [Column("FROM", TypeName = "nvarchar(512)")]
+#if NET
+    public string From { get; init; } = string.Empty;
+#else
+    public string From { get; set; } = string.Empty;
+#endif
+
+    /// <summary>
+    /// Recipient addresses (To header).
+    /// </summary>
+    [Column("TO", TypeName = "nvarchar(max)")]
+#if NET
+    public List<string> To { get; init; } = [];
+#else
+    public List<string> To { get; set; } = [];
+#endif
+
+    /// <summary>
+    /// CC addresses.
+    /// </summary>
+    [Column("CC", TypeName = "nvarchar(max)")]
+#if NET
+    public List<string> Cc { get; init; } = [];
+#else
+    public List<string> Cc { get; set; } = [];
+#endif
+
+    /// <summary>
+    /// Email subject.
+    /// </summary>
+    [MaxLength(998)]
+    [Column("SUBJECT", TypeName = "nvarchar(998)")]
+#if NET
+    public string Subject { get; init; } = string.Empty;
+#else
+    public string Subject { get; set; } = string.Empty;
+#endif
+
+    /// <summary>
+    /// Plain-text body (may be empty when only HTML is present).
+    /// </summary>
+    [Column("TEXT_BODY", TypeName = "nvarchar(max)")]
+#if NET
+    public string TextBody { get; init; } = string.Empty;
+#else
+    public string TextBody { get; set; } = string.Empty;
+#endif
+
+    /// <summary>
+    /// HTML body (may be empty when only plain-text is present).
+    /// </summary>
+    [Column("HTML_BODY", TypeName = "nvarchar(max)")]
+#if NET
+    public string HtmlBody { get; init; } = string.Empty;
+#else
+    public string HtmlBody { get; set; } = string.Empty;
+#endif
+
+    /// <summary>
+    /// Date/time the message was sent (Date header).
+    /// </summary>
+    [Column("DATE", TypeName = "datetime2")]
+#if NET
+    public DateTime Date { get; init; }
+#else
+    public DateTime Date { get; set; }
+#endif
+
+    /// <summary>
+    /// Whether the message has been marked as seen/read on the server.
+    /// </summary>
+    [Column("IS_SEEN", TypeName = "bit")]
+#if NET
+    public bool IsSeen { get; init; }
+#else
+    public bool IsSeen { get; set; }
+#endif
+
+    [ForeignKey(nameof(Account))]
+    [Column("ACCOUNT_ID", TypeName = "int")]
+#if NET
+    public int AccountId { get; init; }
+#else
+    public int AccountId { get; set; }
+#endif
+
+    /// <summary>
+    /// Attachments included with this message.
+    /// </summary>
+#if NET
+    public IEnumerable<EmailAttachment>? Attachments { get; init; }
+#else
+    public IEnumerable<EmailAttachment>? Attachments { get; set; }
+#endif
+
+#if NET
+    public EmailAccount? Account { get; init; }
+#else
+    public EmailAccount? Account { get; set; }
+#endif
+
+#if NET
+    public required string Folder { get; init; }
+#else
+    public string Folder { get; set; } = null!;
+#endif
+}

src/core/DigitalData.MessagingService.Domain/Exceptions/BadRequestException.cs

@@ -0,0 +1,21 @@
+namespace DigitalData.MessagingService.Domain.Exceptions
+{
+    /// <summary>
+    /// Exception thrown when a requested entity is not found.
+    /// </summary>
+    public class BadRequestException : Exception
+    {
+        public BadRequestException(string entityName, object key) : base($"{entityName} with key '{key}' was not found.")
+        {
+        }
+
+        public BadRequestException(string message) : base(message)
+        {
+        }
+
+        public BadRequestException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+        }
+    }
+}

src/core/DigitalData.MessagingService.Publisher.Abstraction/DigitalData.MessagingService.Publisher.Abstraction.csproj

@@ -1,10 +0,0 @@
-<Project Sdk="Microsoft.NET.Sdk">
-
-  <PropertyGroup>
-	<TargetFrameworks>net462;net480;net8.0</TargetFrameworks>
-    <ImplicitUsings>enable</ImplicitUsings>
-    <Nullable>enable</Nullable>
-    <LangVersion>latest</LangVersion>
-  </PropertyGroup>
-
-</Project>

src/core/DigitalData.MessagingService.Publisher.Abstraction/IOutgoingEmailPublisher.cs

@@ -1,14 +0,0 @@
-using System.Threading;
-using System.Threading.Tasks;
-
-namespace DigitalData.MessagingService.Publisher.Abstraction;
-
-/// <summary>
-/// Email queue interface for outgoing emails.
-/// </summary>
-public interface IOutgoingEmailPublisher
-{
-    Task EnqueueAsync(OutgoingEmailEvent outgoingEmailEvent, CancellationToken cancellationToken = default);
-
-    Task<int> GetQueueDepthAsync(CancellationToken cancellationToken = default);
-}

src/infrastructure/DigitalData.MessagingService.Infrastructure/DependencyInjection.cs

@@ -1,10 +1,16 @@
+using AutoMapper;
 using DigitalData.MessagingService.Application.Common.Interfaces;
+using DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
+using DigitalData.MessagingService.Infrastructure.Mappings;
+using DigitalData.MessagingService.Infrastructure.Persistence;
 using DigitalData.MessagingService.Infrastructure.Queue;
+using DigitalData.MessagingService.Infrastructure.Repositories;
 using DigitalData.MessagingService.Infrastructure.Services;
 using DigitalData.MessagingService.Infrastructure.Services.Background;
 using DigitalData.MessagingService.Publisher;
 using DigitalData.MessagingService.RabbitMQ;
 using Microsoft.AspNetCore.DataProtection;
+using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 
@@ -23,8 +29,12 @@ public static class DependencyInjection
         IConfiguration configuration)
     {
         // --- External Services ---
-        // Email Service (using Limilabs Mail.dll - Singleton for use in EmailSenderWorker)
+        // Email Service - SMTP outbound (Limilabs Mail.dll)
         services.AddSingleton<IEmailService, LimilabsEmailService>();
+
+        // Email Service - IMAP inbound (Limilabs Mail.dll)
+        // Fresh connection per call — stateless and thread-safe.
+        services.AddScoped<IImapEmailService, LimilabsImapEmailService>();
         
         // PDF Processing Service (using DevExpress.Pdf)
         services.AddScoped<IPdfProcessingService, DevExpressPdfProcessingService>();
@@ -33,7 +43,7 @@ public static class DependencyInjection
         services.AddSingleton<IEncryptionService, DataProtectionEncryptionService>();
 
         // --- Email Queue (RabbitMQ) ---
-        services.AddSingleton<OutgoingEmailConsumer>();
+        services.AddSingleton<SendingEmailConsumerPool>();
         services.AddMessagingServicePublisher();
 
         // --- RabbitMQ Configuration ---
@@ -46,7 +56,22 @@ public static class DependencyInjection
 
         // Register Background Workers
         services.AddHostedService<AsyncInitWorker>();
+        services.AddHostedService<EmailSyncWorker>();
+
+        services.AddMemoryCache();
+
+        // --- Database (InMemory) ---
+        services.AddDbContext<MessagingServiceDbContext>(options =>
+            options.UseInMemoryDatabase("MessagingServiceDb"));
+
+        services.AddScoped(typeof(IRepository<>), typeof(Repository<>));
+
+        services.AddScoped<IReceivedEmailRepository, ReceivedEmailRepository>();
+
+        // AutoMapper - Register entity self-mappings (T -> T) for generic repository
+        services.AddAutoMapper(config => config.AddMaps(typeof(EntitySelfMappingProfile).Assembly));
 
         return services;
     }
 }
+

src/infrastructure/DigitalData.MessagingService.Infrastructure/DigitalData.MessagingService.Infrastructure.csproj

@@ -25,6 +25,7 @@
     <PackageReference Include="Microsoft.Extensions.Hosting" Version="10.0.10" />
     <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="10.0.10" />
     <PackageReference Include="Microsoft.Identity.Client" Version="4.65.0" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.InMemory" Version="8.0.11" />
     <PackageReference Include="RabbitMQ.Client" Version="7.2.1" />
     <PackageReference Include="System.Text.Encoding.CodePages" Version="10.0.10" />
   </ItemGroup>

src/infrastructure/DigitalData.MessagingService.Infrastructure/Mappings/EntitySelfMappingProfile.cs

@@ -0,0 +1,19 @@
+using AutoMapper;
+using DigitalData.MessagingService.Domain.Entities;
+
+namespace DigitalData.MessagingService.Infrastructure.Mappings;
+
+/// <summary>
+/// AutoMapper profile that registers self-mappings (T -> T) for all domain entities.
+/// This allows AutoMapper to be used uniformly in the generic repository
+/// regardless of whether TDto is a DTO or the entity type itself.
+/// </summary>
+public class EntitySelfMappingProfile : Profile
+{
+    public EntitySelfMappingProfile()
+    {
+        CreateMap<EmailAccount, EmailAccount>();
+        CreateMap<ReceivedEmail, ReceivedEmail>();
+        CreateMap<EmailAttachment, EmailAttachment>();
+    }
+}

src/infrastructure/DigitalData.MessagingService.Infrastructure/Persistence/MessagingServiceDbContext.cs

@@ -1,11 +1,38 @@
+using DigitalData.MessagingService.Domain.Entities;
 using Microsoft.EntityFrameworkCore;
 
 namespace DigitalData.MessagingService.Infrastructure.Persistence;
 
 /// <summary>
 /// Entity Framework Core DbContext for MessagingService.
-/// IMPORTANT: This context maps to a LEGACY database - NO schema modifications allowed!
 /// </summary>
 public class MessagingServiceDbContext(DbContextOptions<MessagingServiceDbContext> options) : DbContext(options)
 {
+    public DbSet<EmailAccount> EmailAccounts => Set<EmailAccount>();
+    public DbSet<ReceivedEmail> ReceivedEmails => Set<ReceivedEmail>();
+    public DbSet<EmailAttachment> EmailAttachments => Set<EmailAttachment>();
+
+    protected override void OnModelCreating(ModelBuilder modelBuilder)
+    {
+        base.OnModelCreating(modelBuilder);
+
+        modelBuilder.Entity<EmailAccount>(entity =>
+        {
+            entity.Property(e => e.Username)
+                  .UseCollation("SQL_Latin1_General_CP1_CI_AS");
+        });
+
+        modelBuilder.Entity<ReceivedEmail>(entity =>
+        {
+            entity.HasMany(e => e.Attachments)
+                  .WithOne(a => a.Email)
+                  .HasForeignKey(a => a.EmailId)
+                  .OnDelete(DeleteBehavior.Cascade);
+
+            entity.HasOne(e => e.Account)
+                  .WithMany()
+                  .HasForeignKey(e => e.AccountId)
+                  .OnDelete(DeleteBehavior.Restrict);
+        });
+    }
 }

src/infrastructure/DigitalData.MessagingService.Infrastructure/Queue/SendingEmailConsumer.cs

@@ -1,60 +1,71 @@
 using System.Text;
 using System.Text.Json;
 using DigitalData.MessagingService.Application.Common.Interfaces;
-using DigitalData.MessagingService.Publisher.Abstraction;
 using DigitalData.MessagingService.RabbitMQ;
 using Microsoft.Extensions.Logging;
-using Microsoft.Extensions.Options;
 using RabbitMQ.Client;
 using RabbitMQ.Client.Events;
+using DigitalData.MessagingService.Application.Common.Dto;
 
 namespace DigitalData.MessagingService.Infrastructure.Queue;
 
 /// <summary>
-/// RabbitMQ-based email queue implementation for outgoing emails.
-/// Provides message persistence, scalability, and reliability.
-/// Uses Lazy<T> initialization pattern to avoid blocking constructor.
+/// A single RabbitMQ consumer that processes one email message at a time on its own dedicated channel.
+/// Multiple instances run in parallel via <see cref="SendingEmailConsumerPool"/> (competing consumers pattern).
+/// Each instance owns exactly one channel — channels are not thread-safe and must not be shared.
 /// </summary>
-public sealed class OutgoingEmailConsumer : IAsyncDisposable
+public sealed class SendingEmailConsumer : IAsyncDisposable
 {
-    private readonly RabbitMqConfiguration _config;
+    private readonly string _queueName;
 
     private readonly Lazy<Task<IChannel>> _lazyChannel;
 
     private readonly Lazy<Task> _lazyInit;
 
-    private readonly ILogger<OutgoingEmailConsumer>? _logger;
+    private readonly ILogger<SendingEmailConsumer>? _logger;
 
-    public OutgoingEmailConsumer(IOptions<RabbitMqConfiguration> config, IEmailService EmailService, RabbitMqConnectionFactory CnnFactory, ILogger<OutgoingEmailConsumer>? logger = null)
+    /// <summary>
+    /// Transient identifier assigned to this consumer instance at runtime.
+    /// A new value is generated each time the application starts or a new consumer is created.
+    /// Use this to correlate log entries belonging to the same consumer session across competing instances.
+    /// </summary>
+    public Guid RuntimeId { get; } = Guid.NewGuid();
+
+    public SendingEmailConsumer(string queueName, IEmailService emailService, RabbitMqConnectionFactory cnnFactory, ILogger<SendingEmailConsumer>? logger = null)
     {
         _logger = logger;
-        _config = config.Value;
+        _queueName = queueName;
 
-        _lazyChannel = new(CnnFactory.CreateChannelAsync);
-        _lazyInit = new(async () => {
+        _lazyChannel = new(cnnFactory.CreateChannelAsync);
+        _lazyInit = new(async () =>
+        {
             var channel = await _lazyChannel.Value;
 
+            // prefetchCount=1 ensures this consumer processes one message at a time before acking.
+            // Parallelism comes from running multiple consumer instances, not from within a single channel.
+            await channel.BasicQosAsync(prefetchSize: 0, prefetchCount: 1, global: false);
+
             var consumer = new AsyncEventingBasicConsumer(channel);
 
             consumer.ReceivedAsync += async (sender, args) =>
             {
-                OutgoingEmailEvent? oMailEvent = null;
+                SendingEmailEvent? oMailEvent = null;
                 try
                 {
                     var json = Encoding.UTF8.GetString(args.Body.ToArray());
-                    oMailEvent = JsonSerializer.Deserialize<OutgoingEmailEvent>(json);
+                    oMailEvent = JsonSerializer.Deserialize<SendingEmailEvent>(json);
 
                     if (oMailEvent is not null)
                     {
                         // Send email via SMTP (SMTP config is injected in IEmailService via IOptions)
-                        await EmailService.SendEmailAsync(
-                            oMailEvent.Recipient,
-                            oMailEvent.Subject,
-                            oMailEvent.Body,
-                            isHtml: oMailEvent.IsHtml);
+                        await emailService.SendEmailAsync(oMailEvent.Mail, args.CancellationToken);
 
                         // Acknowledge message after successful processing
                         await channel.BasicAckAsync(args.DeliveryTag, false, args.CancellationToken);
+
+                        logger?.LogDebug(
+                            "Email successfully sent and acknowledged. RuntimeId={RuntimeId}, Queue={QueueName}, DeliveryTag={DeliveryTag}, To={Recipients}, Subject={Subject}, EventId={EventId}",
+                            RuntimeId, _queueName, args.DeliveryTag, oMailEvent.Mail.Recipients, oMailEvent.Mail.Subject, oMailEvent.Id);
                     }
                     else
                     {
@@ -64,11 +75,11 @@ public sealed class OutgoingEmailConsumer : IAsyncDisposable
                 }
                 catch (Exception ex)
                 {
-                    logger?.LogError(ex, "Failed to process email [To={To}, Subject={Subject}] message: DeliveryTag={DeliveryTag}. Moving to DLQ (NO retry).", oMailEvent?.Recipient, oMailEvent?.Subject, args.DeliveryTag);
+                    logger?.LogError(ex, "Failed to process email [To={To}, Subject={Subject}] message: DeliveryTag={DeliveryTag}. Moving to DLQ (NO retry).", oMailEvent?.Mail.Recipients, oMailEvent?.Mail.Subject, args.DeliveryTag);
 
                     // TODO: Error Reporting Strategy
                     // Option 1: Separate RabbitMQ Queue (emailprofiler.errors)
-                    //   - Create EmailErrorReport entity { OutgoingEmailEventId, Exception, StackTrace, Timestamp, RetryAttempt }
+                    //   - Create EmailErrorReport entity { SendingEmailEventId, Exception, StackTrace, Timestamp, RetryAttempt }
                     //   - Publish to error queue: await _errorQueue.EnqueueAsync(errorReport)
                     //   - Separate worker processes error queue → Log to DB/File/External monitoring
                     //
@@ -93,24 +104,23 @@ public sealed class OutgoingEmailConsumer : IAsyncDisposable
 
             // Start consuming messages (event-driven, non-blocking)
             await channel.BasicConsumeAsync(
-                queue: _config.QueueName,
+                queue: _queueName,
                 autoAck: false,
                 consumer: consumer,
-                cancellationToken: CnnFactory.CancellationToken);
+                cancellationToken: cnnFactory.CancellationToken);
 
-            logger?.LogInformation("RabbitMQ consumer started for queue: {QueueName}", _config.QueueName);
+            logger?.LogInformation("RabbitMQ consumer started for queue: {QueueName}", _queueName);
         });
     }
 
     /// <summary>
-    /// Initialize RabbitMQ connection, channel, exchanges, and queues asynchronously.
-    /// Start event-driven consumer that processes messages as they arrive
-    /// Called lazily on first use via EnsureInitializedAsync.
+    /// Starts the consumer: opens a channel, sets QoS, and registers the event handler.
+    /// Called by <see cref="SendingEmailConsumerPool.InitAsync"/>.
     /// </summary>
     public async Task InitAsync()
     {
         if (_lazyInit.IsValueCreated)
-            _logger?.LogWarning("OutgoingEmailConsumer already initialized. InitAsync() called multiple times.");
+            _logger?.LogWarning("SendingEmailConsumer already initialized. InitAsync() called multiple times.");
 
         await _lazyInit.Value;
     }

src/infrastructure/DigitalData.MessagingService.Infrastructure/Queue/SendingEmailConsumerPool.cs

@@ -0,0 +1,51 @@
+using DigitalData.MessagingService.Application.Common.Interfaces;
+using DigitalData.MessagingService.RabbitMQ;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+
+namespace DigitalData.MessagingService.Infrastructure.Queue;
+
+/// <summary>
+/// Manages a pool of <see cref="SendingEmailConsumer"/> instances that compete for messages
+/// on the same RabbitMQ queue (competing consumers pattern).
+/// Each consumer owns a dedicated channel, so they process messages fully in parallel
+/// without any shared locking or synchronization primitives.
+/// </summary>
+public sealed class SendingEmailConsumerPool : IAsyncDisposable
+{
+    private readonly List<SendingEmailConsumer> _consumers;
+    private readonly ILogger<SendingEmailConsumerPool>? _logger;
+    private readonly int _concurrency;
+
+    public SendingEmailConsumerPool(
+        IOptions<RabbitMqConfiguration> config,
+        IEmailService emailService,
+        RabbitMqConnectionFactory cnnFactory,
+        ILogger<SendingEmailConsumerPool>? logger = null,
+        ILogger<SendingEmailConsumer>? consumerLogger = null)
+    {
+        _logger = logger;
+        _concurrency = config.Value.ConsumerConcurrency;
+
+        _consumers = [.. Enumerable
+            .Range(0, _concurrency)
+            .Select(_ => new SendingEmailConsumer(config.Value.QueueName, emailService, cnnFactory, consumerLogger))];
+    }
+
+    /// <summary>
+    /// Starts all consumers in parallel. Each consumer opens its own channel and begins listening.
+    /// </summary>
+    public async Task InitAsync()
+    {
+        _logger?.LogInformation("Starting {Count} competing email consumers.", _concurrency);
+
+        await Task.WhenAll(_consumers.Select(c => c.InitAsync()));
+
+        _logger?.LogInformation("All {Count} email consumers started.", _concurrency);
+    }
+
+    public async ValueTask DisposeAsync()
+    {
+        await Task.WhenAll(_consumers.Select(async c => await c.DisposeAsync().AsTask()));
+    }
+}

src/infrastructure/DigitalData.MessagingService.Infrastructure/Repositories/ReceivedEmailRepository.cs

@@ -0,0 +1,83 @@
+using AutoMapper;
+using DigitalData.MessagingService.Application.Common.Dto.MailSearch;
+using DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
+using DigitalData.MessagingService.Domain.Entities;
+using DigitalData.MessagingService.Infrastructure.Persistence;
+using Microsoft.EntityFrameworkCore;
+
+namespace DigitalData.MessagingService.Infrastructure.Repositories;
+
+public class ReceivedEmailRepository(MessagingServiceDbContext Context, IMapper Mapper) : Repository<ReceivedEmail>(Context, Mapper), IReceivedEmailRepository
+{
+    public async Task<IEnumerable<ReceivedEmail>> FindAsync(MailSearchFilter mailSearchFilter, EmailAccount? accountQuery = null, CancellationToken cancellationToken = default)
+    {
+        var query = DbSet.AsNoTracking();
+
+        // ── Account filter ─────────────────────────────────────────────────────
+        if (accountQuery is not null)
+            query = query.Where(x => x.AccountId == accountQuery.Id);
+
+        // ── Flag filters ───────────────────────────────────────────────────────
+        if (mailSearchFilter.UnseenOnly)
+            query = query.Where(x => !x.IsSeen);
+
+        // ── Text filters ───────────────────────────────────────────────────────
+        if (!string.IsNullOrWhiteSpace(mailSearchFilter.SubjectContains))
+            query = query.Where(x => x.Subject.Contains(mailSearchFilter.SubjectContains));
+
+        if (!string.IsNullOrWhiteSpace(mailSearchFilter.SenderContains))
+            query = query.Where(x => x.From.Contains(mailSearchFilter.SenderContains));
+
+        if (!string.IsNullOrWhiteSpace(mailSearchFilter.BodyContains))
+            query = query.Where(x => x.TextBody.Contains(mailSearchFilter.BodyContains)
+                                  || x.HtmlBody.Contains(mailSearchFilter.BodyContains));
+
+        // ── UID filter ─────────────────────────────────────────────────────────
+        if (mailSearchFilter.Uid is { } uid)
+        {
+            if (uid.Absolute.HasValue)
+                query = query.Where(x => x.Uid == uid.Absolute.Value);
+            else
+            {
+                if (uid.Min.HasValue)
+                    query = query.Where(x => x.Uid >= uid.Min.Value);
+                if (uid.Max.HasValue)
+                    query = query.Where(x => x.Uid <= uid.Max.Value);
+            }
+        }
+
+        // ── Date filter ────────────────────────────────────────────────────────
+        if (mailSearchFilter.Date is { } date)
+        {
+            if (date.After.HasValue)
+                query = query.Where(x => x.Date >= date.After.Value);
+            if (date.Before.HasValue)
+                query = query.Where(x => x.Date <= date.Before.Value);
+        }
+
+        // ── Attachments ────────────────────────────────────────────────────────
+        if (mailSearchFilter.WithAttachments)
+            query = query.Include(x => x.Attachments);
+
+        // ── Sort ───────────────────────────────────────────────────────────────
+        query = mailSearchFilter.SortOrder == MailSortOrder.OldestFirst
+            ? query.OrderBy(x => x.Date)
+            : query.OrderByDescending(x => x.Date);
+
+        // ── Limit ──────────────────────────────────────────────────────────────
+        if (mailSearchFilter.MaxCount.HasValue)
+            query = query.Take(mailSearchFilter.MaxCount.Value);
+
+        // ── RecipientContains: To/Cc are IEnumerable<string> (nvarchar(max)) ──
+        // EF Core cannot translate collection predicates on these columns to SQL.
+        // Materialization is deferred until after other DB-side filters narrow the set.
+        var results = await query.ToListAsync(cancellationToken);
+
+        if (!string.IsNullOrWhiteSpace(mailSearchFilter.RecipientContains))
+            results = [.. results
+                .Where(x => x.To.Any(t => t.Contains(mailSearchFilter.RecipientContains, StringComparison.OrdinalIgnoreCase))
+                          || x.Cc.Any(c => c.Contains(mailSearchFilter.RecipientContains, StringComparison.OrdinalIgnoreCase)))];
+
+        return results;
+    }
+}

src/infrastructure/DigitalData.MessagingService.Infrastructure/Repositories/Repository.cs

@@ -1,6 +1,6 @@
 using System.Linq.Expressions;
 using AutoMapper;
-using DigitalData.MessagingService.Application.Common.Interfaces;
+using DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
 using DigitalData.MessagingService.Domain.Exceptions;
 using DigitalData.MessagingService.Infrastructure.Persistence;
 using Microsoft.EntityFrameworkCore;
@@ -13,28 +13,36 @@ namespace DigitalData.MessagingService.Infrastructure.Repositories;
 /// </summary>
 public class Repository<TEntity>(MessagingServiceDbContext Context, IMapper Mapper) : IRepository<TEntity> where TEntity : class
 {
-    private readonly DbSet<TEntity> _dbSet = Context.Set<TEntity>();
+    protected readonly DbSet<TEntity> DbSet = Context.Set<TEntity>();
 
     // --- CREATE ---
 
     public async Task<TEntity> CreateAsync<TDto>(TDto dto, CancellationToken cancellationToken = default)
     {
         var entity = Mapper.Map<TEntity>(dto);
-        await _dbSet.AddAsync(entity, cancellationToken);
+        await DbSet.AddAsync(entity, cancellationToken);
         await Context.SaveChangesAsync(cancellationToken);
         return entity;
     }
 
+    public async Task<IEnumerable<TEntity>> CreateRangeAsync<TDto>(IEnumerable<TDto> dtos, CancellationToken cancellationToken = default)
+    {
+        var entities = Mapper.Map<IEnumerable<TEntity>>(dtos);
+        await DbSet.AddRangeAsync(entities, cancellationToken);
+        await Context.SaveChangesAsync(cancellationToken);
+        return entities;
+    }
+
     // --- READ ---
 
     public async Task<TEntity?> GetByIdAsync(int id, CancellationToken cancellationToken = default)
     {
-        return await _dbSet.FindAsync([id], cancellationToken);
+        return await DbSet.FindAsync([id], cancellationToken);
     }
 
     public async Task<IEnumerable<TEntity>> GetAllAsync(CancellationToken cancellationToken = default)
     {
-        return await _dbSet.ToListAsync(cancellationToken);
+        return await DbSet.ToListAsync(cancellationToken);
     }
 
     public async Task<IEnumerable<TEntity>> FindAsync(
@@ -43,14 +51,14 @@ public class Repository<TEntity>(MessagingServiceDbContext Context, IMapper Mapp
         int? take = null,
         CancellationToken cancellationToken = default)
     {
-        var query = _dbSet.Where(predicate);
-        
+        var query = DbSet.Where(predicate);
+
         if (skip.HasValue)
             query = query.Skip(skip.Value);
-        
+
         if (take.HasValue)
             query = query.Take(take.Value);
-        
+
         return await query.ToListAsync(cancellationToken);
     }
 
@@ -58,14 +66,14 @@ public class Repository<TEntity>(MessagingServiceDbContext Context, IMapper Mapp
         Expression<Func<TEntity, bool>> predicate,
         CancellationToken cancellationToken = default)
     {
-        return await _dbSet.FirstOrDefaultAsync(predicate, cancellationToken);
+        return await DbSet.FirstOrDefaultAsync(predicate, cancellationToken);
     }
 
     public async Task<TEntity?> FindSingleAsync(
         Expression<Func<TEntity, bool>> predicate,
         CancellationToken cancellationToken = default)
     {
-        return await _dbSet.SingleOrDefaultAsync(predicate, cancellationToken);
+        return await DbSet.SingleOrDefaultAsync(predicate, cancellationToken);
     }
 
     public async Task<int> CountAsync(
@@ -73,15 +81,68 @@ public class Repository<TEntity>(MessagingServiceDbContext Context, IMapper Mapp
         CancellationToken cancellationToken = default)
     {
         return predicate == null
-            ? await _dbSet.CountAsync(cancellationToken)
-            : await _dbSet.CountAsync(predicate, cancellationToken);
+            ? await DbSet.CountAsync(cancellationToken)
+            : await DbSet.CountAsync(predicate, cancellationToken);
     }
 
     public async Task<bool> AnyAsync(
         Expression<Func<TEntity, bool>> predicate,
         CancellationToken cancellationToken = default)
     {
-        return await _dbSet.AnyAsync(predicate, cancellationToken);
+        return await DbSet.AnyAsync(predicate, cancellationToken);
+    }
+
+    // --- UPSERT ---
+
+    /// <summary>
+    /// Upsert: if no record matches the predicate, creates a new entity;
+    /// if one or more match, updates the FIRST match.
+    /// Returns the entity and a flag indicating whether it was created (true) or updated (false).
+    /// Auto-saves changes.
+    /// </summary>
+    public async Task<(TEntity Entity, bool Created)> UpsertAsync<TDto>(
+        Expression<Func<TEntity, bool>> predicate,
+        TDto dto,
+        CancellationToken cancellationToken = default)
+    {
+        var entity = await DbSet.FirstOrDefaultAsync(predicate, cancellationToken);
+
+        if (entity is null)
+        {
+            entity = Mapper.Map<TEntity>(dto);
+            await DbSet.AddAsync(entity, cancellationToken);
+            await Context.SaveChangesAsync(cancellationToken);
+            return (entity, true);
+        }
+
+        Mapper.Map(dto, entity);
+        await Context.SaveChangesAsync(cancellationToken);
+        return (entity, false);
+    }
+
+    /// <summary>
+    /// Upsert (single-safe): if no record matches the predicate, creates a new entity;
+    /// if exactly one matches, updates it. Throws InvalidOperationException if 2+ match.
+    /// Auto-saves changes.
+    /// </summary>
+    public async Task<(TEntity Entity, bool Created)> UpsertSingleAsync<TDto>(
+        Expression<Func<TEntity, bool>> predicate,
+        TDto dto,
+        CancellationToken cancellationToken = default)
+    {
+        var entity = await DbSet.SingleOrDefaultAsync(predicate, cancellationToken);
+
+        if (entity is null)
+        {
+            entity = Mapper.Map<TEntity>(dto);
+            await DbSet.AddAsync(entity, cancellationToken);
+            await Context.SaveChangesAsync(cancellationToken);
+            return (entity, true);
+        }
+
+        Mapper.Map(dto, entity);
+        await Context.SaveChangesAsync(cancellationToken);
+        return (entity, false);
     }
 
     // --- UPDATE ---
@@ -96,7 +157,7 @@ public class Repository<TEntity>(MessagingServiceDbContext Context, IMapper Mapp
         TDto dto,
         CancellationToken cancellationToken = default)
     {
-        var entity = await _dbSet.SingleOrDefaultAsync(predicate, cancellationToken) 
+        var entity = await DbSet.SingleOrDefaultAsync(predicate, cancellationToken)
             ?? throw new NotFoundException($"No {typeof(TEntity).Name} found matching the predicate.");
         Mapper.Map(dto, entity);
         await Context.SaveChangesAsync(cancellationToken);
@@ -112,13 +173,8 @@ public class Repository<TEntity>(MessagingServiceDbContext Context, IMapper Mapp
         TDto dto,
         CancellationToken cancellationToken = default)
     {
-        var entities = await _dbSet.Where(predicate).ToListAsync(cancellationToken);
-
-        foreach (var entity in entities)
-        {
-            Mapper.Map(dto, entity);
-        }
-
+        var entities = await DbSet.Where(predicate).ToListAsync(cancellationToken);
+        entities.ForEach(entity => Mapper.Map(dto, entity));
         await Context.SaveChangesAsync(cancellationToken);
         return entities.Count;
     }
@@ -134,9 +190,9 @@ public class Repository<TEntity>(MessagingServiceDbContext Context, IMapper Mapp
         Expression<Func<TEntity, bool>> predicate,
         CancellationToken cancellationToken = default)
     {
-        var entity = await _dbSet.SingleOrDefaultAsync(predicate, cancellationToken) 
+        var entity = await DbSet.SingleOrDefaultAsync(predicate, cancellationToken)
             ?? throw new NotFoundException($"No {typeof(TEntity).Name} found matching the predicate.");
-        _dbSet.Remove(entity);
+        DbSet.Remove(entity);
         await Context.SaveChangesAsync(cancellationToken);
     }
 
@@ -149,9 +205,8 @@ public class Repository<TEntity>(MessagingServiceDbContext Context, IMapper Mapp
         Expression<Func<TEntity, bool>> predicate,
         CancellationToken cancellationToken = default)
     {
-        var entities = await _dbSet.Where(predicate).ToListAsync(cancellationToken);
-
-        _dbSet.RemoveRange(entities);
+        var entities = await DbSet.Where(predicate).ToListAsync(cancellationToken);
+        DbSet.RemoveRange(entities);
         await Context.SaveChangesAsync(cancellationToken);
         return entities.Count;
     }

src/infrastructure/DigitalData.MessagingService.Infrastructure/Services/Background/AsyncInitWorker.cs

@@ -1,19 +1,18 @@
-using DigitalData.MessagingService.Application.Common.Interfaces;
 using DigitalData.MessagingService.Infrastructure.Queue;
 using Microsoft.Extensions.Hosting;
 
 namespace DigitalData.MessagingService.Infrastructure.Services.Background;
 
 /// <summary>
-/// A hosted background service responsible for initializing the outgoing email queue consumer.
+/// A hosted background service responsible for initializing the competing email consumer pool.
 /// Leverages a push-based, event-driven RabbitMQ consumer to eliminate polling overhead.
 /// Email account configuration is resolved exclusively from application settings; no database access is performed.
 /// </summary>
-public class AsyncInitWorker(OutgoingEmailConsumer EmailConsumer) : BackgroundService
+public class AsyncInitWorker(SendingEmailConsumerPool ConsumerPool) : BackgroundService
 {
     protected override async Task ExecuteAsync(CancellationToken stoppingToken)
     {
-        await EmailConsumer.InitAsync();
+        await ConsumerPool.InitAsync();
 
         await Task.Delay(Timeout.Infinite, stoppingToken).ConfigureAwait(ConfigureAwaitOptions.SuppressThrowing);
     }

src/infrastructure/DigitalData.MessagingService.Infrastructure/Services/Background/EmailSyncWorker.cs

@@ -0,0 +1,61 @@
+using DigitalData.MessagingService.Application.Common.Interfaces;
+using DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
+using DigitalData.MessagingService.Application.Common.Options;
+using DigitalData.MessagingService.Domain.Entities;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+
+namespace DigitalData.MessagingService.Infrastructure.Services.Background;
+
+public class EmailSyncWorker(IOptions<EmailAccountsOptions> Options, IServiceProvider Provider, ILogger<EmailSyncWorker> Logger) : BackgroundService
+{
+    private readonly string DefaultFolder = "INBOX";
+
+    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+    {
+        await UpsertSeedEmailAccount(stoppingToken);
+
+        var interval = TimeSpan.FromSeconds(Options.Value.SyncIntervalSeconds);
+
+        while (!stoppingToken.IsCancellationRequested)
+        {
+            using var scope = Provider.CreateAsyncScope();
+
+            var emailAccountRepo = scope.ServiceProvider.GetRequiredService<IRepository<EmailAccount>>();
+
+            var imapService = scope.ServiceProvider.GetRequiredService<IImapEmailService>();
+
+            foreach (var account in await emailAccountRepo.GetAllAsync(stoppingToken))
+                if (account.ImapServer is not null)
+                {
+                    Logger.LogDebug("Email synchronization has started for account {username} in folder {folder}.", account.Username, DefaultFolder);
+                    
+                    try
+                    {
+                        var res = await imapService.SyncEmailsAsync(account, DefaultFolder, stoppingToken);
+                        Logger.LogDebug("Email synchronization has completed for account {username} in folder {folder}. Processed: {processedCount}, Failed: {failedCount}", account.Username, DefaultFolder, res.ProcessedCount, res.FailedCount);
+                    }
+                    catch(Exception ex)
+                    {
+                        // Log the exception or handle it as needed
+                        Logger.LogError(ex, "Error syncing emails for account {username}", account.Username);
+                    }
+                }
+
+            await Task.Delay(interval, stoppingToken).ConfigureAwait(ConfigureAwaitOptions.SuppressThrowing);
+        }
+    }
+
+    public async Task UpsertSeedEmailAccount(CancellationToken stoppingToken)
+    {
+        using var scope = Provider.CreateAsyncScope();
+
+        var emailAccountRepo = scope.ServiceProvider.GetRequiredService<IRepository<EmailAccount>>();
+
+        // init seed email accounts if not exist
+        foreach (var account in Options.Value.Accounts)
+            await emailAccountRepo.UpsertAsync(a => a.Username == account.Username, account, stoppingToken);
+    }
+}

src/infrastructure/DigitalData.MessagingService.Infrastructure/Services/Extensions/CacheExtensions.cs

@@ -0,0 +1,24 @@
+using Microsoft.Extensions.Caching.Memory;
+
+namespace DigitalData.MessagingService.Infrastructure.Services.Extensions;
+
+public static class CacheExtensions
+{
+    private readonly static string ImapCacheKeyPrefix = Guid.NewGuid().ToString();
+
+    private static string CreateImapLastSyncDateCacheKey(int accountId, string folder)
+    {
+        return $"{ImapCacheKeyPrefix}_{accountId}_{folder}_LastImapSyncDate";
+    }
+
+    public static DateTime? GetLastImapSyncDate(this IMemoryCache cache, int accountId, string folder)
+    {
+        return cache.Get<DateTime?>(CreateImapLastSyncDateCacheKey(accountId, folder));
+    }
+
+    public static void SetLastImapSyncDate(this IMemoryCache cache, int accountId, string folder, DateTime date)
+    {
+        var key = CreateImapLastSyncDateCacheKey(accountId, folder);
+        cache.Set(key, date);
+    }
+}

src/infrastructure/DigitalData.MessagingService.Infrastructure/Services/Extensions/ImapExtensions.cs

@@ -0,0 +1,16 @@
+using Limilabs.Client.IMAP;
+
+namespace DigitalData.MessagingService.Infrastructure.Services.Extensions;
+
+public static class ImapExtensions
+{
+    public static async Task CloseSafelyAsync(this Imap imap)
+    {
+        try
+        {
+            if (imap.Connected)
+                await imap.CloseAsync();
+        }
+        catch { /* Ignore disconnect errors */ }
+    }
+}

src/infrastructure/DigitalData.MessagingService.Infrastructure/Services/Extensions/SmtpExtensions.cs

@@ -0,0 +1,16 @@
+using Limilabs.Client.SMTP;
+
+namespace DigitalData.MessagingService.Infrastructure.Services.Extensions;
+
+public static class SmtpExtensions
+{
+    public static async Task CloseSafelyAsync(this Smtp smtp)
+    {
+        try
+        {
+            if (smtp.Connected)
+                await smtp.CloseAsync();
+        }
+        catch { /* Ignore disconnect errors */ }
+    }
+}

src/infrastructure/DigitalData.MessagingService.Infrastructure/Services/LimilabsEmailService.cs

@@ -1,111 +1,140 @@
 using System.Text;
-using DigitalData.MessagingService.Application.Common.Dtos;
 using DigitalData.MessagingService.Application.Common.Interfaces;
 using DigitalData.MessagingService.Domain.Exceptions;
 using Limilabs.Client.SMTP;
 using Limilabs.Mail;
 using Limilabs.Mail.Headers;
-using Microsoft.Extensions.Options;
+using DigitalData.MessagingService.Infrastructure.Services.Extensions;
+using DigitalData.MessagingService.Application.Common.Dto;
+using DigitalData.MessagingService.Domain.Entities;
 
 namespace DigitalData.MessagingService.Infrastructure.Services;
 
 /// <summary>
 /// Email service using Limilabs Mail.dll for SMTP operations (send-only).
 /// Commercial-grade library with superior Exchange support.
-/// SMTP configuration is injected via IOptions&lt;EmailAccountDto&gt; from appsettings.json.
+/// SMTP configuration is injected via IOptions&lt;EmailAccountsOptions&gt; from appsettings.json.
+/// Uses the first account in the list whose <see cref="EmailAccount.Name"/> equals <c>"default"</c>,
+/// or falls back to the first account if none is named "default".
 /// </summary>
-public class LimilabsEmailService(
-    IEncryptionService encryptionService,
-    IOptions<EmailAccountDto> smtpConfig) : IEmailService
+public class LimilabsEmailService() : IEmailService
 {
-    private readonly EmailAccountDto _smtpAccount = smtpConfig.Value;
-
     // Register encoding provider for Limilabs (requires windows-1252 and other code pages)
     static LimilabsEmailService()
     {
         Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
     }
 
-    public async Task SendEmailAsync(string to, string subject, string body, bool isHtml = true, CancellationToken cancellationToken = default)
+    public async Task SendEmailAsync(EmailContext context, CancellationToken cancellationToken = default)
     {
         using var smtp = new Smtp();
-
+        ISendMessageResult? result = null;
         try
         {
-            await ConnectAndAuthenticateSmtpAsync(smtp);
+            await ConnectAndAuthenticateSmtpAsync(smtp, context.Sender);
 
             var builder = new MailBuilder();
-            builder.From.Add(new MailBox(_smtpAccount.Username));
-            builder.To.Add(new MailBox(to));
-            builder.Subject = subject;
+            builder.From.Add(new MailBox(context.Sender.Username));
 
-            if (isHtml)
-            {
-                builder.Html = body;
-            }
+            foreach (var recipient in context.Recipients)
+                builder.To.Add(new MailBox(recipient));
+
+            builder.Subject = context.Subject;
+
+            if (context.IsHtml)
+                builder.Html = context.Body;
             else
-            {
-                builder.Text = body;
-            }
+                builder.Text = context.Body;
+
+            AddAttachments(builder, context.Attachments);
 
             var mail = builder.Create();
 
-            var result = smtp.SendMessage(mail);
+            result = await smtp.SendMessageAsync(mail, cancellationToken);
 
             if (result.Status != SendMessageStatus.Success)
             {
-                throw new InvalidOperationException($"Failed to send email. Status: {result.Status}");
+                throw new InvalidOperationException($"Failed to send email. Status: {result.Status}. {ErrorMessageBuilder(result)}");
             }
 
-            smtp.Close();
-            await Task.CompletedTask; // For async consistency
+            await smtp.CloseAsync(cancellationToken);
         }
         catch (Limilabs.Client.ServerException ex)
         {
-            DisconnectSafely(smtp);
-            throw new AuthenticationFailedException("SMTP authentication failed. Check credentials or OAuth2 configuration.", ex);
+            await smtp.CloseSafelyAsync();
+            throw new AuthenticationFailedException($"SMTP authentication failed. Check credentials or OAuth2 configuration. {ErrorMessageBuilder(result)}", ex);
         }
         catch (Exception ex)
         {
-            DisconnectSafely(smtp);
-            throw new InvalidOperationException("Failed to send email via SMTP server.", ex);
+            await smtp.CloseSafelyAsync();
+            throw new InvalidOperationException($"Failed to send email via SMTP server. {ErrorMessageBuilder(result)}", ex);
         }
     }
 
-    // --- Private Helper Methods ---
-
-    private async Task ConnectAndAuthenticateSmtpAsync(Smtp smtp)
+    private static async Task ConnectAndAuthenticateSmtpAsync(Smtp smtp, EmailAccount smtpAccount)
     {
-        if (_smtpAccount.SmtpUseSsl)
+        if (smtpAccount.SmtpUseSsl)
         {
-            smtp.ConnectSSL(_smtpAccount.SmtpServer, _smtpAccount.SmtpPort);
+            await smtp.ConnectSSLAsync(smtpAccount.SmtpServer, smtpAccount.SmtpPort);
         }
         else
         {
-            smtp.Connect(_smtpAccount.SmtpServer, _smtpAccount.SmtpPort);
+            await smtp.ConnectAsync(smtpAccount.SmtpServer, smtpAccount.SmtpPort);
         }
 
-        if (_smtpAccount.UseOAuth2)
+        if (smtpAccount.UseOAuth2)
         {
             throw new NotSupportedException("OAuth2 is not configured for this SMTP account. UseOAuth2 must be false.");
         }
         else
         {
-            var password = _smtpAccount.PasswordEncrypted ? encryptionService.Decrypt(_smtpAccount.Password) : _smtpAccount.Password;
-
-            smtp.Login(_smtpAccount.Username, password);
+            await smtp.LoginAsync(smtpAccount.Username, smtpAccount.Password);
         }
-
-        await Task.CompletedTask; // For async consistency
     }
 
-    private static void DisconnectSafely(Smtp smtp)
+    private static string ErrorMessageBuilder(ISendMessageResult? result = null)
     {
-        try
+        if(result is null || result.GeneralErrors.Count == 0)
+            return string.Empty;
+        else if(result.GeneralErrors.Count == 1)
+            return $"Error: {result.GeneralErrors.FirstOrDefault()}";
+
+        var message = new StringBuilder("Errors:\n");
+
+        foreach (var error in result.GeneralErrors)
         {
-            if (smtp.Connected)
-                smtp.Close();
+            message.AppendLine($"   • {error}");
         }
-        catch { /* Ignore disconnect errors */ }
+
+        return message.ToString();
     }
-}
+
+    private static void AddAttachments(MailBuilder builder, IEnumerable<EmailAttachmentDto> attachments)
+    {
+        foreach (var attachment in attachments)
+        {
+            if (attachment.IsInline)
+            {
+                var visual = builder.AddVisual(attachment.Content);
+                visual.FileName = attachment.FileName;
+                visual.ContentId = string.IsNullOrWhiteSpace(attachment.ContentId)
+                    ? attachment.FileName
+                    : attachment.ContentId;
+
+                if (!string.IsNullOrWhiteSpace(attachment.ContentType))
+                    visual.ContentType = ContentType.Parse(attachment.ContentType);
+            }
+            else
+            {
+                var part = builder.AddAttachment(attachment.Content);
+                part.FileName = attachment.FileName;
+
+                if (!string.IsNullOrWhiteSpace(attachment.ContentType))
+                    part.ContentType = ContentType.Parse(attachment.ContentType);
+
+                if (!string.IsNullOrWhiteSpace(attachment.ContentId))
+                    part.ContentId = attachment.ContentId;
+            }
+        }
+    }
+}

src/infrastructure/DigitalData.MessagingService.Infrastructure/Services/LimilabsImapEmailService.cs

@@ -0,0 +1,189 @@
+using DigitalData.MessagingService.Application.Common.Dto;
+using DigitalData.MessagingService.Application.Common.Interfaces;
+using DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
+using DigitalData.MessagingService.Domain.Entities;
+using DigitalData.MessagingService.Infrastructure.Services.Extensions;
+using Limilabs.Client.IMAP;
+using Limilabs.Mail;
+using Microsoft.Extensions.Logging;
+using System.Collections.Concurrent;
+using System.Text;
+
+namespace DigitalData.MessagingService.Infrastructure.Services;
+
+/// <summary>
+/// IMAP email service using Limilabs Mail.dll.
+/// Opens a fresh connection per call — stateless and thread-safe.
+/// </summary>
+public class LimilabsImapEmailService(ILogger<LimilabsImapEmailService> Logger, IRepository<ReceivedEmail> Repository) : IImapEmailService
+{
+    private static readonly string CacheKeyPrefix = Guid.NewGuid().ToString();
+
+    static LimilabsImapEmailService()
+    {
+        Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
+    }
+
+    // Public API
+    public async Task<EmailSyncResult> SyncEmailsAsync(EmailAccount account, string folder = "INBOX", CancellationToken cancel = default)
+    {
+        using var imap = await OpenAsync(account, folder, cancel);
+        try
+        {
+            #region Find UIDs
+            // Server-side: only date range; all other filters are applied in-process after cache retrieval
+            List<ICriterion> criterions = [];
+
+            var since = GetLastImapSyncDate(account.Id, folder);
+
+            if (since is not null && since != default)
+                criterions.Add(Expression.SentSince(since.Value));
+
+            var searchExpression = criterions.Count > 0 ? Expression.And([.. criterions]) : Expression.All();
+
+            var operationStartTime = DateTime.UtcNow;
+
+            List<long> uids = [.. await imap.SearchAsync(searchExpression, cancel)];
+            #endregion
+            
+            if (uids.Count == 0)
+                return new EmailSyncResult();
+            
+            var emails = new List<ReceivedEmailDto>(uids.Count);
+
+            var failedCount = 0;
+
+            foreach (var uid in uids)
+            {
+                if (await Repository.AnyAsync(x => x.Uid == uid, cancel))
+                    continue;
+
+                cancel.ThrowIfCancellationRequested();
+
+                try
+                {
+                    #region Read email
+                    var eml = await imap.GetMessageByUIDAsync(uid, cancel);
+                    var mail = new MailBuilder().CreateFromEml(eml);
+                    var flags = await imap.GetFlagsByUIDAsync(uid, cancel);
+
+                    var attachments = new List<EmailAttachmentDto>();
+
+                    foreach (var att in mail.Attachments)
+                    {
+                        attachments.Add(new EmailAttachmentDto
+                        {
+                            FileName = att.FileName ?? "attachment",
+                            Content = att.Data,
+                            ContentType = att.ContentType?.ToString() ?? "application/octet-stream",
+                            IsInline = false,
+                            ContentId = att.ContentId
+                        });
+                    }
+
+                    foreach (var vis in mail.Visuals)
+                    {
+                        attachments.Add(new EmailAttachmentDto
+                        {
+                            FileName = vis.FileName ?? "inline",
+                            Content = vis.Data,
+                            ContentType = vis.ContentType?.ToString() ?? "application/octet-stream",
+                            IsInline = true,
+                            ContentId = vis.ContentId
+                        });
+                    }
+
+                    var email = new ReceivedEmailDto
+                    {
+                        Uid = uid,
+                        AccountId = account.Id,
+                        From = mail.From.FirstOrDefault()?.Address ?? string.Empty,
+                        To = [.. mail.To.SelectMany(m => m.GetMailboxes()).Select(mb => mb.Address)],
+                        Cc = [.. mail.Cc.SelectMany(m => m.GetMailboxes()).Select(mb => mb.Address)],
+                        Subject = mail.Subject ?? string.Empty,
+                        TextBody = mail.Text ?? string.Empty,
+                        HtmlBody = mail.Html ?? string.Empty,
+                        Date = mail.Date ?? DateTime.MinValue,
+                        IsSeen = flags.Contains(Flag.Seen),
+                        Attachments = attachments,
+                        Folder = folder
+                    };
+                    #endregion Read email
+
+                    emails.Add(email);
+
+                    SetLastImapSyncDate(account.Id, folder, operationStartTime);
+                }
+                catch (Exception ex)
+                {
+                    failedCount += 1;
+                    Logger.LogWarning(ex,
+                        "Failed to fetch IMAP message UID={Uid} from folder {Folder}. Skipping.",
+                        uid, folder);
+                }
+            }
+
+            await imap.CloseAsync(cancel);
+
+            await Repository.CreateRangeAsync(emails, cancel);
+
+            return new EmailSyncResult(ProcessedCount: emails.Count, FailedCount: failedCount);
+        }
+        catch
+        {
+            await imap.CloseSafelyAsync();
+            throw;
+        }
+    }
+
+    public async Task MarkAsSeenAsync(EmailAccount account, long uid, string folder = "INBOX", CancellationToken cancel = default)
+    {
+        using var imap = await OpenAsync(account, folder, cancel);
+        try
+        {
+            await imap.MarkMessageSeenByUIDAsync(uid, cancel);
+            await imap.CloseAsync(cancel);
+        }
+        catch
+        {
+            await imap.CloseSafelyAsync();
+            throw;
+        }
+    }
+
+    private static async Task<Imap> OpenAsync(EmailAccount account, string folder = "INBOX", CancellationToken cancel = default)
+    {
+        var imap = new Imap();
+
+        if (account.ImapUseSsl)
+            await imap.ConnectSSLAsync(account.ImapServer!, account.ImapPort, cancel: cancel);
+        else
+            await imap.ConnectAsync(account.ImapServer!, account.ImapPort, cancel: cancel);
+
+        await imap.LoginAsync(account.Username, account.Password, cancel);
+
+        if (string.Equals(folder, "INBOX", StringComparison.OrdinalIgnoreCase))
+            await imap.SelectInboxAsync(cancel);
+        else
+            await imap.SelectAsync(folder, cancel);
+
+        return imap;
+    }
+
+    #region IMAP Last Sync Date Cache
+    private readonly ConcurrentDictionary<ImapCacheKey, DateTime> _cache = new();
+
+    private record ImapCacheKey(int AccountId, string Folder);
+
+    public DateTime? GetLastImapSyncDate(int accountId, string folder = "INBOX")
+    {
+        return _cache.GetValueOrDefault(new ImapCacheKey(accountId, folder));
+    }
+
+    private void SetLastImapSyncDate(int accountId, string folder, DateTime date)
+    {
+        var key = new ImapCacheKey(accountId, folder);
+        _cache[key] = date;
+    }
+    #endregion
+}

src/infrastructure/DigitalData.MessagingService.Publisher/DependencyInjection.cs

@@ -1,6 +1,5 @@
-using DigitalData.MessagingService.Publisher.Abstraction;
+using DigitalData.MessagingService.Application.Common.Interfaces;
 using DigitalData.MessagingService.RabbitMQ;
-using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 
 namespace DigitalData.MessagingService.Publisher;
@@ -13,7 +12,7 @@ public static class DependencyInjection
             services.AddRabbitMqConnectionFactory(configure);
 
         // --- Email Queue (RabbitMQ) ---
-        services.AddSingleton<IOutgoingEmailPublisher, OutgoingEmailPublisher>();
+        services.AddSingleton<ISendingEmailPublisher, SendingEmailPublisher>();
 
         return services;
     }

src/infrastructure/DigitalData.MessagingService.Publisher/DigitalData.MessagingService.Publisher.csproj

@@ -12,7 +12,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <ProjectReference Include="..\..\core\DigitalData.MessagingService.Publisher.Abstraction\DigitalData.MessagingService.Publisher.Abstraction.csproj" />
+    <ProjectReference Include="..\..\core\DigitalData.MessagingService.Application\DigitalData.MessagingService.Application.csproj" />
     <ProjectReference Include="..\DigitalData.MessagingService.RabbitMQ\DigitalData.MessagingService.RabbitMQ.csproj" />
   </ItemGroup>
 

src/infrastructure/DigitalData.MessagingService.Publisher/SendingEmailPublisher.cs

@@ -4,7 +4,8 @@ using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
 using RabbitMQ.Client;
 using DigitalData.MessagingService.RabbitMQ;
-using DigitalData.MessagingService.Publisher.Abstraction;
+using DigitalData.MessagingService.Application.Common.Dto;
+using DigitalData.MessagingService.Application.Common.Interfaces;
 
 namespace DigitalData.MessagingService.Publisher;
 
@@ -13,14 +14,14 @@ namespace DigitalData.MessagingService.Publisher;
 /// Provides message persistence, scalability, and reliability.
 /// Uses Lazy<T> initialization pattern to avoid blocking constructor.
 /// </summary>
-public sealed class OutgoingEmailPublisher : IOutgoingEmailPublisher, IAsyncDisposable
+public sealed class SendingEmailPublisher : ISendingEmailPublisher, IAsyncDisposable
 {
     private readonly RabbitMqConfiguration _config;
-    private readonly ILogger<OutgoingEmailPublisher> _logger;
+    private readonly ILogger<SendingEmailPublisher> _logger;
     private readonly RabbitMqConnectionFactory _cnnFactory;
     private readonly Lazy<Task<IChannel>> _lazyChannel;
 
-    public OutgoingEmailPublisher(IOptions<RabbitMqConfiguration> config, ILogger<OutgoingEmailPublisher> logger, RabbitMqConnectionFactory cnnFactory)
+    public SendingEmailPublisher(IOptions<RabbitMqConfiguration> config, ILogger<SendingEmailPublisher> logger, RabbitMqConnectionFactory cnnFactory)
     {
         _config = config.Value;
         _logger = logger;
@@ -66,9 +67,9 @@ public sealed class OutgoingEmailPublisher : IOutgoingEmailPublisher, IAsyncDisp
         return channel;
     }
     
-    public async Task EnqueueAsync(OutgoingEmailEvent outgoingEmailEvent, CancellationToken cancellationToken = default)
+    public async Task EnqueueAsync(SendingEmailEvent sendingEmailEvent, CancellationToken cancellationToken = default)
     {
-        var json = JsonSerializer.Serialize(outgoingEmailEvent);
+        var json = JsonSerializer.Serialize(sendingEmailEvent);
         var body = Encoding.UTF8.GetBytes(json);
 
         var properties = new BasicProperties

src/infrastructure/DigitalData.MessagingService.RabbitMQ/RabbitMqConfiguration.cs

@@ -75,5 +75,11 @@ namespace DigitalData.MessagingService.RabbitMQ
         /// Routing key used to bind <see cref="DlqQueueName"/> to <see cref="DlqExchangeName"/>.
         /// </summary>
         public string DlqRoutingKey { get; set; } = "email.outbox.dlq";
+
+        /// <summary>
+        /// Maximum number of email messages processed concurrently by the consumer.
+        /// Maps directly to RabbitMQ prefetchCount. Recommended: 3–5.
+        /// </summary>
+        public ushort ConsumerConcurrency { get; set; } = 5;
     }
 }

src/presentation/DigitalData.MessagingService.API/Controllers/EmailAccountController.cs

@@ -0,0 +1,27 @@
+using DigitalData.MessagingService.Application.EmailAccounts.Queries;
+using MediatR;
+using Microsoft.AspNetCore.Mvc;
+
+namespace DigitalData.MessagingService.API.Controllers;
+
+/// <summary>
+/// 
+/// </summary>
+[Route("api/[controller]")]
+[ApiController]
+public class EmailAccountController(IMediator mediator) : ControllerBase
+{
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <param name="query"></param>
+    /// <param name="cancellationToken"></param>
+    /// <returns></returns>
+    [HttpGet]
+    [ProducesResponseType(StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<IActionResult> GetEmailAccount([FromQuery] GetEmailAccountQuery query, CancellationToken cancellationToken)
+    {
+        return Ok(await mediator.Send(query, cancellationToken));
+    }
+}

src/presentation/DigitalData.MessagingService.API/Controllers/EmailController.cs

@@ -0,0 +1,115 @@
+using DigitalData.MessagingService.Application.EmailSending.Commands;
+using DigitalData.MessagingService.Application.EmailReceiving.Queries;
+using MediatR;
+using Microsoft.AspNetCore.Mvc;
+using DigitalData.MessagingService.Application.Common.Dto;
+
+namespace DigitalData.MessagingService.API.Controllers;
+
+/// <summary>
+/// Email sending API controller.
+/// Enqueues outgoing emails to RabbitMQ for async processing.
+/// </summary>
+[ApiController]
+[Route("api/[controller]")]
+public class EmailController(IMediator mediator) : ControllerBase
+{
+    /// <summary>
+    /// 
+    /// </summary>
+    public enum OnlyFilter
+    {
+        /// <summary>
+        /// 
+        /// </summary>
+        HtmlBody,
+        /// <summary>
+        /// 
+        /// </summary>
+        Uid,
+    }
+
+    #region Send
+    /// <summary>
+    /// Send an email, optionally with file attachments.
+    /// Omit the <c>attachments</c> field for a plain send.
+    /// </summary>
+    /// <param name="command">Email fields as form values</param>
+    /// <param name="attachments">Optional uploaded files</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>HTTP 202 Accepted with the queued event ID</returns>
+    [HttpPost]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(StatusCodes.Status202Accepted)]
+    [ProducesResponseType(StatusCodes.Status400BadRequest)]
+    public async Task<IActionResult> SendEmail(
+        [FromForm] PublishEmailCommand command,
+        IFormFileCollection? attachments,
+        CancellationToken cancellationToken)
+    {
+        var commandWithAttachments = command.WithAttachments(
+            await BuildAttachmentsAsync(attachments, cancellationToken));
+
+        var eventId = await mediator.Send(commandWithAttachments, cancellationToken);
+        return Accepted(new { Id = eventId });
+    }
+
+    private static async Task<IEnumerable<EmailAttachmentDto>> BuildAttachmentsAsync(
+        IFormFileCollection? files,
+        CancellationToken cancellationToken)
+    {
+        if (files is null || files.Count == 0)
+            return [];
+
+        var result = new List<EmailAttachmentDto>(files.Count);
+
+        foreach (var file in files)
+        {
+            using var ms = new MemoryStream();
+            await file.CopyToAsync(ms, cancellationToken);
+
+            result.Add(new EmailAttachmentDto
+            {
+                FileName    = file.FileName,
+                Content     = ms.ToArray(),
+                ContentType = file.ContentType
+            });
+        }
+
+        return result;
+    }
+    #endregion Send
+
+    #region Receive
+    /// <summary>
+    /// Fetch emails from an IMAP mailbox.
+    /// </summary>
+    /// <param name="query">Query parameters for filtering and fetching emails from the IMAP mailbox.</param>
+    /// <param name="only"></param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>HTTP 200 with list of received emails.</returns>
+    [HttpGet]
+    [ProducesResponseType(StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<IActionResult> FetchEmails([FromQuery] ReadEmailQuery query, [FromQuery] OnlyFilter? only = null, CancellationToken cancellationToken = default)
+    {
+        var emails = await mediator.Send(query, cancellationToken);
+
+        if(!emails.Any())
+            return NotFound("No emails found matching the specified criteria.");
+
+        if (only == OnlyFilter.HtmlBody)
+        {
+            if (emails.FirstOrDefault()?.HtmlBody is string htmlBody)
+                return Content(htmlBody, "text/html");
+            else
+                return NotFound();
+        }
+        else if (only == OnlyFilter.Uid)
+            return Ok(emails.Select(e => e.Uid).ToList());
+        else
+            return Ok(emails);
+    }
+    #endregion Receive
+}

src/presentation/DigitalData.MessagingService.API/Controllers/EmailsController.cs

@@ -1,36 +0,0 @@
-using DigitalData.MessagingService.Application.EmailSending.Commands;
-using MediatR;
-using Microsoft.AspNetCore.Mvc;
-
-namespace DigitalData.MessagingService.API.Controllers;
-
-/// <summary>
-/// Email sending API controller
-/// Enqueues outgoing emails to RabbitMQ for async processing
-/// </summary>
-[ApiController]
-[Route("api/[controller]")]
-public class EmailsController(IMediator mediator) : ControllerBase
-{
-    /// <summary>
-    /// Send email (enqueue to RabbitMQ for background processing)
-    /// </summary>
-    /// <param name="command">Send email command</param>
-    /// <param name="cancellationToken">Cancellation token</param>
-    /// <returns>HTTP 202 Accepted (queued for processing)</returns>
-    [HttpPost("send")]
-    [ProducesResponseType(StatusCodes.Status202Accepted)]
-    [ProducesResponseType(StatusCodes.Status400BadRequest)]
-    public async Task<IActionResult> SendEmail([FromBody] SendEmailCommand command, CancellationToken cancellationToken)
-    {
-        var outgoingEmailEvent = await mediator.Send(command, cancellationToken);
-
-        return Accepted(new
-        {
-            CommandId = outgoingEmailEvent.Id,
-            To = outgoingEmailEvent.Recipient,
-            outgoingEmailEvent.Subject,
-            outgoingEmailEvent.QueuedAt
-        });
-    }
-}

src/presentation/DigitalData.MessagingService.API/DigitalData.MessagingService.API.csproj

@@ -1,29 +1,43 @@
-<Project Sdk="Microsoft.NET.Sdk.Web">
+<Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFrameworks>net8.0</TargetFrameworks>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
-	<UserSecretsId>dotnet-DigitalData.MessagingService.Service-e7ef6a9a-436f-48a1-b4f6-ec9381c8cb47</UserSecretsId>
+    <GenerateDocumentationFile>true</GenerateDocumentationFile>
+    <PackageId>DigitalData.MessagingService.API</PackageId>
+    <Title></Title>
+    <Authors>Digital Data GmbH</Authors>
+    <Company>Digital Data GmbH</Company>
+    <Product>DigitalData.MessagingService.API</Product>
+    <Version>1.0.0-beta</Version>
+    <FileVersion>1.0.0.0</FileVersion>
+    <AssemblyVersion>1.0.0.0</AssemblyVersion>
+    <Copyright>Copyright © 2026 Digital Data GmbH. All rights reserved.</Copyright>
+	<DocumentationFile>bin\$(Configuration)\$(TargetFramework)\$(AssemblyName).xml</DocumentationFile>
   </PropertyGroup>
 
   <ItemGroup>
     <PackageReference Include="Serilog.AspNetCore" Version="10.0.0" />
+    <PackageReference Include="Serilog.Settings.Configuration" Version="10.0.1" />
     <PackageReference Include="Serilog.Sinks.Console" Version="6.1.1" />
     <PackageReference Include="Serilog.Sinks.File" Version="7.0.0" />
+    <PackageReference Include="Serilog.Sinks.SQLite" Version="7.0.0" />
+    <PackageReference Include="Serilog.UI" Version="3.2.0" />
+    <PackageReference Include="Serilog.UI.SqliteProvider" Version="1.1.0" />
     <PackageReference Include="Swashbuckle.AspNetCore" Version="6.6.2" />
 	<PackageReference Include="Microsoft.Extensions.Hosting" Version="10.0.10" />
 	<PackageReference Include="System.Security.Cryptography.Xml" Version="10.0.10" />
   </ItemGroup>
 
-  <ItemGroup>
-    <Folder Include="Properties\" />
-  </ItemGroup>
-
   <ItemGroup>
     <ProjectReference Include="..\..\core\DigitalData.MessagingService.Application\DigitalData.MessagingService.Application.csproj" />
     <ProjectReference Include="..\..\core\DigitalData.MessagingService.Domain\DigitalData.MessagingService.Domain.csproj" />
     <ProjectReference Include="..\..\infrastructure\DigitalData.MessagingService.Infrastructure\DigitalData.MessagingService.Infrastructure.csproj" />
   </ItemGroup>
 
+  <ItemGroup>
+    <Folder Include="Infrastructure\Swagger\" />
+  </ItemGroup>
+
 </Project>

src/presentation/DigitalData.MessagingService.API/Middleware/ExceptionHandlingMiddleware.cs

@@ -1,89 +1,82 @@
 using System.Net;
 using System.Text.Json;
 using DigitalData.MessagingService.Domain.Exceptions;
+using FluentValidation;
 
 namespace DigitalData.MessagingService.API.Middleware;
 
 /// <summary>
 /// Global exception handling middleware
 /// </summary>
-public class ExceptionHandlingMiddleware
+public class ExceptionHandlingMiddleware(RequestDelegate Next, ILogger<ExceptionHandlingMiddleware> Logger)
 {
     private static readonly JsonSerializerOptions _jsonSerializerOptions = new()
     {
         PropertyNamingPolicy = JsonNamingPolicy.CamelCase
     };
 
-    private readonly RequestDelegate _next;
-    private readonly ILogger<ExceptionHandlingMiddleware> _logger;
-
-    public ExceptionHandlingMiddleware(
-        RequestDelegate next,
-        ILogger<ExceptionHandlingMiddleware> logger)
-    {
-        _next = next;
-        _logger = logger;
-    }
-
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <param name="context"></param>
+    /// <returns></returns>
     public async Task InvokeAsync(HttpContext context)
     {
         try
         {
-            await _next(context);
+            await Next(context);
         }
         catch (Exception ex)
         {
-            await HandleExceptionAsync(context, ex);
+            context.Response.ContentType = "application/json";
+
+            var (statusCode, message) = ex switch
+            {
+                NotFoundException notFoundEx =>
+                    (HttpStatusCode.NotFound, notFoundEx.Message),
+
+                BadRequestException badRequestEx =>
+                    (HttpStatusCode.BadRequest, badRequestEx.Message),
+
+                AuthenticationFailedException authEx =>
+                    (HttpStatusCode.Unauthorized, authEx.Message),
+
+                ValidationException validationEx =>
+                    (HttpStatusCode.BadRequest, FormatValidationErrors(validationEx)),
+
+                _ => (HttpStatusCode.InternalServerError, "An internal server error occurred")
+            };
+
+            context.Response.StatusCode = (int)statusCode;
+
+            // Log the exception
+            if (statusCode == HttpStatusCode.InternalServerError)
+            {
+                Logger.LogError(ex, "Unhandled exception: {Message}", ex.Message);
+            }
+            else
+            {
+                Logger.LogWarning(ex, "Exception handled: {StatusCode} - {Message}",
+                    statusCode, message);
+            }
+
+            var response = new
+            {
+                StatusCode = (int)statusCode,
+                Message = message,
+                DetailedMessage = statusCode == HttpStatusCode.InternalServerError
+                    ? ex.Message
+                    : null,
+                Timestamp = DateTime.Now
+            };
+
+            var json = JsonSerializer.Serialize(response, _jsonSerializerOptions);
+
+            await context.Response.WriteAsync(json);
         }
     }
 
-    private async Task HandleExceptionAsync(HttpContext context, Exception exception)
-    {
-        context.Response.ContentType = "application/json";
-
-        var (statusCode, message) = exception switch
-        {
-            NotFoundException notFoundEx => 
-                (HttpStatusCode.NotFound, notFoundEx.Message),
-            
-            AuthenticationFailedException authEx => 
-                (HttpStatusCode.Unauthorized, authEx.Message),
-                        
-            FluentValidation.ValidationException validationEx =>
-                (HttpStatusCode.BadRequest, FormatValidationErrors(validationEx)),
-            
-            _ => (HttpStatusCode.InternalServerError, "An internal server error occurred")
-        };
-
-        context.Response.StatusCode = (int)statusCode;
-
-        // Log the exception
-        if (statusCode == HttpStatusCode.InternalServerError)
-        {
-            _logger.LogError(exception, "Unhandled exception: {Message}", exception.Message);
-        }
-        else
-        {
-            _logger.LogWarning(exception, "Exception handled: {StatusCode} - {Message}", 
-                statusCode, message);
-        }
-
-        var response = new
-        {
-            StatusCode = (int)statusCode,
-            Message = message,
-            DetailedMessage = statusCode == HttpStatusCode.InternalServerError 
-                ? exception.Message 
-                : null,
-            Timestamp = DateTime.Now
-        };
-
-        var json = JsonSerializer.Serialize(response, _jsonSerializerOptions);
-
-        await context.Response.WriteAsync(json);
-    }
-
-    private static string FormatValidationErrors(FluentValidation.ValidationException exception)
+    private static string FormatValidationErrors(ValidationException exception)
     {
         var errors = exception.Errors
             .Select(e => $"{e.PropertyName}: {e.ErrorMessage}")

src/presentation/DigitalData.MessagingService.API/Program.cs

@@ -1,17 +1,41 @@
 using DigitalData.MessagingService.API.Middleware;
 using DigitalData.MessagingService.Application;
-using DigitalData.MessagingService.Application.Common.Dtos;
 using DigitalData.MessagingService.Infrastructure;
 using Serilog;
+using Serilog.Ui.Core.Extensions;
+using Serilog.Ui.SqliteDataProvider.Extensions;
+using Serilog.Ui.Web.Extensions;
 
-// Configure Serilog early
+// Build temporary configuration to read log directory early
+var tempConfig = new ConfigurationBuilder()
+    .SetBasePath(Directory.GetCurrentDirectory())
+    .AddJsonFile("appsettings.json", optional: false, reloadOnChange: false)
+    .AddJsonFile("appsettings.Secrets.json", optional: true, reloadOnChange: false)
+    .Build();
+
+var logDirectoryRaw = tempConfig.GetValue<string>("Application:LogDirectory") ?? "logs";
+// Always resolve to an absolute path so sink and UI provider point to the same file
+var logDirectory = Path.IsPathRooted(logDirectoryRaw)
+    ? logDirectoryRaw
+    : Path.Combine(AppContext.BaseDirectory, logDirectoryRaw);
+Directory.CreateDirectory(logDirectory);
+var sqliteDbPath = Path.Combine(logDirectory, "logs.db");
+
+// Configure Serilog early (bootstrap + full pipeline)
 Log.Logger = new LoggerConfiguration()
-    .WriteTo.Console()
+    .MinimumLevel.Information()
+    .MinimumLevel.Override("Microsoft", Serilog.Events.LogEventLevel.Warning)
+    .MinimumLevel.Override("Microsoft.AspNetCore", Serilog.Events.LogEventLevel.Warning)
+    .MinimumLevel.Override("Microsoft.EntityFrameworkCore", Serilog.Events.LogEventLevel.Warning)
+    .MinimumLevel.Override("System", Serilog.Events.LogEventLevel.Warning)
+    .Enrich.FromLogContext()
+    .WriteTo.Console(outputTemplate: "{Timestamp:yyyy-MM-dd HH:mm:ss.fff zzz} [{Level:u3}] {Message:lj}{NewLine}{Exception}")
     .WriteTo.File(
-        path: "logs/emailprofiler-.log",
+        path: Path.Combine(logDirectory, "emailprofiler-.log"),
         rollingInterval: RollingInterval.Day,
         retainedFileCountLimit: 30,
         outputTemplate: "{Timestamp:yyyy-MM-dd HH:mm:ss.fff zzz} [{Level:u3}] {Message:lj}{NewLine}{Exception}")
+    .WriteTo.SQLite(sqliteDbPath, storeTimestampInUtc: true)
     .CreateBootstrapLogger();
 
 try
@@ -25,12 +49,13 @@ try
         .ReadFrom.Configuration(context.Configuration)
         .ReadFrom.Services(services)
         .Enrich.FromLogContext()
-        .WriteTo.Console()
+        .WriteTo.Console(outputTemplate: "{Timestamp:yyyy-MM-dd HH:mm:ss.fff zzz} [{Level:u3}] {Message:lj}{NewLine}{Exception}")
         .WriteTo.File(
-            path: "logs/emailprofiler-.log",
+            path: Path.Combine(logDirectory, "emailprofiler-.log"),
             rollingInterval: RollingInterval.Day,
             retainedFileCountLimit: 30,
-            outputTemplate: "{Timestamp:yyyy-MM-dd HH:mm:ss.fff zzz} [{Level:u3}] {Message:lj}{NewLine}{Exception}"));
+            outputTemplate: "{Timestamp:yyyy-MM-dd HH:mm:ss.fff zzz} [{Level:u3}] {Message:lj}{NewLine}{Exception}")
+        .WriteTo.SQLite(sqliteDbPath, storeTimestampInUtc: true));
 
     // Add appsettings.Secrets.json for sensitive configuration (not committed to git)
     builder.Configuration.AddJsonFile("appsettings.Secrets.json", optional: true, reloadOnChange: true);
@@ -41,15 +66,21 @@ try
     // Register Infrastructure layer (RabbitMQ, Repositories, etc.)
     builder.Services.AddInfrastructure(builder.Configuration);
 
-    // Register EmailAccount configuration (IOptions<EmailAccountDto>)
-    builder.Services.Configure<EmailAccountDto>(
-        builder.Configuration.GetSection("EmailAccount"));
-
     builder.Services.AddControllers();
 
     builder.Services.AddEndpointsApiExplorer();
     builder.Services.AddSwaggerGen();
 
+    // Register Serilog.UI with SQLite provider for web log viewer
+    builder.Services.AddSerilogUi(options =>
+    {
+        options.UseSqliteServer(dbOpt =>
+        {
+            dbOpt.WithConnectionString($"Data Source={sqliteDbPath}");
+            dbOpt.WithTable("Logs");
+        });
+    });
+
     var app = builder.Build();
 
     // Add global exception handling middleware
@@ -58,8 +89,11 @@ try
     // Add Serilog request logging
     app.UseSerilogRequestLogging();
 
-    // Configure the HTTP request pipeline.
-    if (app.Environment.IsDevelopment())
+    // Configure Swagger — enabled in Development always, and in other environments based on appsettings
+    var swaggerEnabled = app.Environment.IsDevelopment()
+        || app.Configuration.GetValue<bool>("Swagger:Enabled");
+
+    if (swaggerEnabled)
     {
         app.UseSwagger();
         app.UseSwaggerUI();
@@ -67,6 +101,9 @@ try
 
     app.UseHttpsRedirection();
 
+    // Serve Serilog.UI log viewer at /serilog-ui
+    app.UseSerilogUi();
+
     app.UseAuthorization();
 
     app.MapControllers();

src/presentation/DigitalData.MessagingService.API/appsettings.Development.json

@@ -4,5 +4,16 @@
       "Default": "Information",
       "Microsoft.AspNetCore": "Warning"
     }
+  },
+  "Serilog": {
+    "MinimumLevel": {
+      "Default": "Debug",
+      "Override": {
+        "Microsoft": "Warning",
+        "Microsoft.AspNetCore": "Warning",
+        "Microsoft.EntityFrameworkCore": "Warning",
+        "System": "Warning"
+      }
+    }
   }
 }

src/presentation/DigitalData.MessagingService.API/appsettings.Secrets.json

@@ -1,27 +0,0 @@
-{
-  "AllowedHosts": "*",
-  "RabbitMQ": {
-    "HostName": "172.24.12.56",
-    "Port": 5672,
-    "UserName": "admin",
-    "Password": "fl!'D}4;pYBb\\VD&{6]]G*\\0Bq8fVIn0j?Sgm\\2A,6GS47g5Dj",
-    "VirtualHost": "/",
-    "AutomaticRecoveryEnabled": true,
-    "NetworkRecoveryIntervalSeconds": 10,
-    "QueueName": "emailprofiler.email.outbox",
-    "ExchangeName": "emailprofiler.emails",
-    "RoutingKey": "email.outbox",
-    "DlqQueueName": "emailprofiler.email.outbox.dlq",
-    "DlqExchangeName": "emailprofiler.emails.dlq",
-    "DlqRoutingKey": "email.outbox.dlq"
-  },
-  "EmailAccount": {
-    "Username": "test-flow@digitaldata.works",
-    "Password": "ddemail108",
-    "PasswordEncrypted": false,
-    "SmtpServer": "kundencenter.triplew.de",
-    "SmtpPort": 465,
-    "SmtpUseSsl": true,
-    "UseOAuth2": false
-  }
-}

src/presentation/DigitalData.MessagingService.API/appsettings.json

@@ -11,6 +11,12 @@
     }
   },
   "AllowedHosts": "*",
+  "Application": {
+    "LogDirectory": "logs"
+  },
+  "Swagger": {
+    "Enabled": true
+  },
   "Workers": {
     "EmailSender": {
       "Enabled": true

src/presentation/DigitalData.MessagingService.Client/DigitalData.MessagingService.Client.csproj

@@ -11,7 +11,7 @@
 		<PackageIcon>icon.png</PackageIcon>
 		<RepositoryUrl>http://git.dd:3000/AppStd/Rec.git</RepositoryUrl>
 		<PackageTags>digital data messaging service api client</PackageTags>
-		<Version>1.0.0-beta</Version>
+		<Version>1.0.0</Version>
 		<AssemblyVersion>1.0.0.0</AssemblyVersion>
 		<FileVersion>1.0.0.0</FileVersion>
 		<Description></Description>
@@ -35,8 +35,12 @@
 	</ItemGroup>
 
 	<ItemGroup>
-	  <ProjectReference Include="..\..\core\DigitalData.MessagingService.Publisher.Abstraction\DigitalData.MessagingService.Publisher.Abstraction.csproj" />
-	  <ProjectReference Include="..\..\infrastructure\DigitalData.MessagingService.Publisher\DigitalData.MessagingService.Publisher.csproj" />
+	  <ProjectReference Include="..\..\infrastructure\DigitalData.MessagingService.Publisher\DigitalData.MessagingService.Publisher.csproj">
+	    <PrivateAssets>all</PrivateAssets>
+	  </ProjectReference>
+	  <ProjectReference Include="..\..\infrastructure\DigitalData.MessagingService.RabbitMQ\DigitalData.MessagingService.RabbitMQ.csproj">
+	    <PrivateAssets>all</PrivateAssets>
+	  </ProjectReference>
 	</ItemGroup>
 
 </Project>

src/presentation/DigitalData.MessagingService.Client/EmailSender.cs

@@ -1,11 +1,10 @@
 using DigitalData.MessagingService.Publisher;
-using DigitalData.MessagingService.Publisher.Abstraction;
 using DigitalData.MessagingService.RabbitMQ;
 using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Extensions.Logging;
-using System;
+using DigitalData.MessagingService.Application.Common.Dto;
+using DigitalData.MessagingService.Application.Common.Interfaces;
 
-namespace DigitalData.MessagingService.Client.DependencyInjection;
+namespace DigitalData.MessagingService.Client;
 
 /// <summary>
 /// Provides a static, self-contained client for sending emails via RabbitMQ
@@ -108,24 +107,30 @@ public static class EmailSender
     }
 
     /// <summary>
-    /// Enqueues the specified email event to the RabbitMQ messaging pipeline.
+    /// Enqueues the specified email to the RabbitMQ messaging pipeline.
     /// </summary>
-    /// <param name="email">The outgoing email event to enqueue.</param>
+    /// <param name="email">The outgoing email data to enqueue.</param>
     /// <exception cref="InvalidOperationException">
     /// Thrown when <see cref="ConnectRabbitMq(Action{RabbitMqConfiguration}, OnReconnect)"/> has not been called prior to sending.
     /// </exception>
     /// <remarks>
-    /// This method resolves <see cref="IOutgoingEmailPublisher"/> from the internal
+    /// This method maps <see cref="EmailContext"/> to <see cref="SendingEmailEvent"/>,
+    /// then resolves <see cref="ISendingEmailPublisher"/> from the internal
     /// service provider and calls <c>EnqueueAsync</c> in a fire-and-forget manner.
     /// Ensure that any unhandled exceptions from the async operation are handled
     /// at the publisher level.
     /// </remarks>
-    public static void Send(OutgoingEmailEvent email)
+    public static void Send(EmailContext email)
     {
         if(!IsConnected)
             throw new InvalidOperationException("Messaging service is not connected. Call ConnectRabbitMq first.");
 
-        var publisher = LazyProvider.Value.GetRequiredService<IOutgoingEmailPublisher>();
-        publisher.EnqueueAsync(email);
+        var publisher = LazyProvider.Value.GetRequiredService<ISendingEmailPublisher>();
+        publisher.EnqueueAsync(new SendingEmailEvent()
+        {
+            Id = Guid.NewGuid(),
+            Mail = email,
+            QueuedAt = DateTime.Now
+        });
     }
 }

src/presentation/DigitalData.MessagingService.Client/OnReconnect.cs

@@ -1,7 +1,7 @@
-namespace DigitalData.MessagingService.Client.DependencyInjection;
+namespace DigitalData.MessagingService.Client;
 
 /// <summary>
-/// Defines the behavior when <see cref="EmailSender.ConnectRabbitMq"/> is called
+/// Defines the behavior when <see cref="EmailSender.ConnectRabbitMq(Action{RabbitMQ.RabbitMqConfiguration}, OnReconnect)"/> is called
 /// while a connection has already been established.
 /// </summary>
 public enum OnReconnect

src/presentation/DigitalData.MessagingService.Client/README.md

@@ -63,30 +63,28 @@ EmailSender.ConnectRabbitMq(
 ### 2. E-Mail versenden
 
 ```csharp
-EmailSender.Send(new OutgoingEmailEvent
+EmailSender.Send(new Email
 {
-    Id        = Guid.NewGuid(),
     Recipient = "empfaenger@beispiel.de",
     Subject   = "Willkommen",
     Body      = "<p>Hallo Welt!</p>",
-    IsHtml    = true,
-    QueuedAt  = DateTime.Now
+    IsHtml    = true
 });
 ```
 
 ```vb
-EmailSender.Send(New OutgoingEmailEvent With {
-    .Id        = Guid.NewGuid(),
+EmailSender.Send(New Email With {
     .Recipient = "empfaenger@beispiel.de",
     .Subject   = "Willkommen",
     .Body      = "<p>Hallo Welt!</p>",
-    .IsHtml    = True,
-    .QueuedAt  = DateTime.Now
+    .IsHtml    = True
 })
 ```
 
 `Send` ist eine **Fire-and-Forget**-Methode: die Nachricht wird in die RabbitMQ-Queue eingereiht und der aufrufende Code wartet nicht auf die eigentliche Zustellung.
 
+> **Hinweis:** `Id` und `QueuedAt` werden intern automatisch gesetzt. Im `Email`-Objekt müssen nur `Recipient`, `Subject`, `Body` und `IsHtml` angegeben werden.
+
 ### 3. Verbindungsstatus prüfen
 
 ```csharp

tests/DigitalData.MessagingService.Tests/DigitalData.MessagingService.Tests.csproj

@@ -23,7 +23,7 @@
   <ItemGroup>
     <ProjectReference Include="..\..\src\infrastructure\DigitalData.MessagingService.Publisher\DigitalData.MessagingService.Publisher.csproj" />
     <ProjectReference Include="..\..\src\infrastructure\DigitalData.MessagingService.RabbitMQ\DigitalData.MessagingService.RabbitMQ.csproj" />
-    <ProjectReference Include="..\..\src\presentation\DigitalData.MessagingService.Client.DependencyInjection\DigitalData.MessagingService.Client.DependencyInjection.csproj" />
+    <ProjectReference Include="..\..\src\presentation\DigitalData.MessagingService.Client\DigitalData.MessagingService.Client.csproj" />
   </ItemGroup>
 
   <ItemGroup>

tests/DigitalData.MessagingService.Tests/Integration/EmailSenderTests.cs

@@ -1,5 +1,6 @@
-using DigitalData.MessagingService.Client.DependencyInjection;
-using DigitalData.MessagingService.Publisher.Abstraction;
+using DigitalData.MessagingService.Application.Common.Dto;
+using DigitalData.MessagingService.Client;
+using DigitalData.MessagingService.Domain.Entities;
 
 namespace DigitalData.MessagingService.Tests.Integration;
 
@@ -75,14 +76,13 @@ public sealed class EmailSenderTests
     [Fact]
     public void Send_WithValidEmail_DoesNotThrow()
     {
-        var email = new OutgoingEmailEvent
+        var email = new EmailContext
         {
-            Id = Guid.NewGuid(),
-            Recipient = "hakanttek@gmail.com",
+            Sender = new EmailAccount { Username = "test@example.com", Password = "password", SmtpServer = "smtp.example.com" },
+            Recipients = ["hakanttek@gmail.com"],
             Subject = "EmailSender.Send Integration Test",
             Body = "<p>Sent via EmailSender static client.</p>",
             IsHtml = true,
-            QueuedAt = DateTime.Now
         };
 
         var exception = Record.Exception(() => EmailSender.Send(email));
@@ -93,14 +93,13 @@ public sealed class EmailSenderTests
     [Fact]
     public void Send_WithPlainTextBody_DoesNotThrow()
     {
-        var email = new OutgoingEmailEvent
+        var email = new EmailContext
         {
-            Id = Guid.NewGuid(),
-            Recipient = "hakanttek@gmail.com",
+            Sender = new EmailAccount { Username = "test@example.com", Password = "password", SmtpServer = "smtp.example.com" },
+            Recipients = ["hakanttek@gmail.com"],
             Subject = "Plain Text Test",
             Body = "This is a plain text email.",
-            IsHtml = false,
-            QueuedAt = DateTime.Now
+            IsHtml = false
         };
 
         var exception = Record.Exception(() => EmailSender.Send(email));

tests/DigitalData.MessagingService.Tests/Integration/EmailSenderUrlOverloadTests.cs

@@ -1,5 +1,6 @@
-using DigitalData.MessagingService.Client.DependencyInjection;
-using DigitalData.MessagingService.Publisher.Abstraction;
+using DigitalData.MessagingService.Application.Common.Dto;
+using DigitalData.MessagingService.Client;
+using DigitalData.MessagingService.Domain.Entities;
 
 namespace DigitalData.MessagingService.Tests.Integration;
 
@@ -55,14 +56,13 @@ public sealed class EmailSenderUrlOverloadTests
     [Fact]
     public void Send_AfterUrlOverloadConnection_DoesNotThrow()
     {
-        var email = new OutgoingEmailEvent
+        var email = new EmailContext
         {
-            Id = Guid.NewGuid(),
-            Recipient = "url-overload-test@example.com",
+            Sender = new EmailAccount { Username = "test@example.com", Password = "password", SmtpServer = "smtp.example.com" },
+            Recipients = ["url-overload-test@example.com"],
             Subject = "URL Overload Integration Test",
             Body = "<p>Sent after URL-based connection.</p>",
-            IsHtml = true,
-            QueuedAt = DateTime.Now
+            IsHtml = true
         };
 
         // Connection was established via Action<> overload in the fixture;

tests/DigitalData.MessagingService.Tests/Integration/SendingEmailPublisherTests.cs

@@ -1,46 +1,50 @@
 using System.Text;
 using System.Text.Json;
 using DigitalData.MessagingService.Publisher;
-using DigitalData.MessagingService.Publisher.Abstraction;
 using DigitalData.MessagingService.RabbitMQ;
 using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Extensions.Logging;
-using RabbitMQ.Client;
+using DigitalData.MessagingService.Application.Common.Dto;
+using DigitalData.MessagingService.Application.Common.Interfaces;
+using DigitalData.MessagingService.Domain.Entities;
 
 namespace DigitalData.MessagingService.Tests.Integration;
 
 /// <summary>
-/// Integration tests for <see cref="OutgoingEmailPublisher"/> against the real RabbitMQ broker.
+/// Integration tests for <see cref="SendingEmailPublisher"/> against the real RabbitMQ broker.
 /// Each test publishes a message and immediately reads it back via BasicGetAsync to verify
 /// the full round-trip without starting the consumer (which requires Limilabs Mail.dll).
 /// </summary>
-public sealed class OutgoingEmailPublisherTests : IAsyncDisposable
+public sealed class SendingEmailPublisherTests : IAsyncDisposable
 {
     private readonly ServiceProvider _serviceProvider;
-    private readonly IOutgoingEmailPublisher _publisher;
+    private readonly ISendingEmailPublisher _publisher;
     private readonly RabbitMqConnectionFactory _factory;
 
-    public OutgoingEmailPublisherTests()
+    public SendingEmailPublisherTests()
     {
         var services = new ServiceCollection();
         services.AddLogging();
         services.AddMessagingServicePublisher(RabbitMqTestConfig.Apply);
 
         _serviceProvider = services.BuildServiceProvider();
-        _publisher = _serviceProvider.GetRequiredService<IOutgoingEmailPublisher>();
+        _publisher = _serviceProvider.GetRequiredService<ISendingEmailPublisher>();
         _factory = _serviceProvider.GetRequiredService<RabbitMqConnectionFactory>();
     }
 
     [Fact]
     public async Task EnqueueAsync_PublishesMessage_MessageArrivesInQueue()
     {
-        var email = new OutgoingEmailEvent
+        var email = new SendingEmailEvent
         {
             Id = Guid.NewGuid(),
-            Recipient = "test@example.com",
-            Subject = "Integration Test - EnqueueAsync",
-            Body = "<p>Hello from integration test.</p>",
-            IsHtml = true,
+            Mail = new EmailContext
+            {
+                Sender = new EmailAccount { Username = "test@example.com", Password = "password", SmtpServer = "smtp.example.com" },
+                Recipients = ["test@example.com"],
+                Subject = "Integration Test - EnqueueAsync",
+                Body = "<p>Hello from integration test.</p>",
+                IsHtml = true,
+            },
             QueuedAt = DateTime.Now
         };
 
@@ -59,13 +63,17 @@ public sealed class OutgoingEmailPublisherTests : IAsyncDisposable
     [Fact]
     public async Task EnqueueAsync_MultipleMessages_AllArrivesInQueue()
     {
-        var emails = Enumerable.Range(1, 3).Select(i => new OutgoingEmailEvent
+        var emails = Enumerable.Range(1, 3).Select(i => new SendingEmailEvent
         {
             Id = Guid.NewGuid(),
-            Recipient = $"recipient{i}@example.com",
-            Subject = $"Integration Test - Batch #{i}",
-            Body = $"Batch message {i}",
-            IsHtml = false,
+            Mail = new EmailContext
+            {
+                Sender = new EmailAccount { Username = "test@example.com", Password = "password", SmtpServer = "smtp.example.com" },
+                Recipients = [$"recipient{i}@example.com"],
+                Subject = $"Integration Test - Batch #{i}",
+                Body = $"Batch message {i}",
+                IsHtml = false,
+            },
             QueuedAt = DateTime.Now
         }).ToList();
 
@@ -82,13 +90,17 @@ public sealed class OutgoingEmailPublisherTests : IAsyncDisposable
     [Fact]
     public async Task GetQueueDepthAsync_AfterPublish_ReturnsPositiveDepth()
     {
-        var email = new OutgoingEmailEvent
+        var email = new SendingEmailEvent
         {
             Id = Guid.NewGuid(),
-            Recipient = "depth-test@example.com",
-            Subject = "Integration Test - GetQueueDepth",
-            Body = "Queue depth test",
-            IsHtml = false,
+            Mail = new EmailContext
+            {
+                Sender = new EmailAccount { Username = "test@example.com", Password = "password", SmtpServer = "smtp.example.com" },
+                Recipients = ["depth-test@example.com"],
+                Subject = "Integration Test - GetQueueDepth",
+                Body = "Queue depth test",
+                IsHtml = false,
+            },
             QueuedAt = DateTime.Now
         };
 
@@ -105,13 +117,17 @@ public sealed class OutgoingEmailPublisherTests : IAsyncDisposable
     {
         var id = Guid.NewGuid();
 
-        var email = new OutgoingEmailEvent
+        var email = new SendingEmailEvent
         {
             Id = id,
-            Recipient = "serialize@example.com",
-            Subject = "Serialization Test",
-            Body = "<strong>Bold</strong>",
-            IsHtml = true,
+            Mail = new EmailContext
+            {
+                Sender = new EmailAccount { Username = "test@example.com", Password = "password", SmtpServer = "smtp.example.com" },
+                Recipients = new List<string> { "serialize@example.com" },
+                Subject = "Serialization Test",
+                Body = "<strong>Bold</strong>",
+                IsHtml = true,
+            },
             QueuedAt = DateTime.Now
         };
 
@@ -123,16 +139,16 @@ public sealed class OutgoingEmailPublisherTests : IAsyncDisposable
 
         Assert.NotNull(received);
         Assert.Equal(id, received.Id);
-        Assert.Equal("serialize@example.com", received.Recipient);
-        Assert.Equal("Serialization Test", received.Subject);
-        Assert.Equal("<strong>Bold</strong>", received.Body);
-        Assert.True(received.IsHtml);
+        Assert.Equal(["serialize@example.com"], received.Mail.Recipients);
+        Assert.Equal("Serialization Test", received.Mail.Subject);
+        Assert.Equal("<strong>Bold</strong>", received.Mail.Body);
+        Assert.True(received.Mail.IsHtml);
     }
 
     /// <summary>
     /// Reads a single message from the queue without acknowledging it (peek via nack+requeue).
     /// </summary>
-    private async Task<OutgoingEmailEvent?> PeekMessageAsync()
+    private async Task<SendingEmailEvent?> PeekMessageAsync()
     {
         var connection = await _factory.GetDefaultConnectionAsync();
         await using var channel = await connection.CreateChannelAsync();
@@ -146,21 +162,21 @@ public sealed class OutgoingEmailPublisherTests : IAsyncDisposable
         await channel.BasicNackAsync(result.DeliveryTag, multiple: false, requeue: true);
 
         var json = Encoding.UTF8.GetString(result.Body.ToArray());
-        return JsonSerializer.Deserialize<OutgoingEmailEvent>(json);
+        return JsonSerializer.Deserialize<SendingEmailEvent>(json);
     }
 
     /// <summary>
     /// Scans queue messages (up to a limit) to find a message matching the given <paramref name="id"/>.
     /// All messages are re-queued after inspection.
     /// </summary>
-    private async Task<OutgoingEmailEvent?> FindMessageAsync(Guid id, int maxMessages = 50)
+    private async Task<SendingEmailEvent?> FindMessageAsync(Guid id, int maxMessages = 50)
     {
         var connection = await _factory.GetDefaultConnectionAsync();
         await using var channel = await connection.CreateChannelAsync();
 
         var requeue = new List<(ulong DeliveryTag, byte[] Body)>();
 
-        OutgoingEmailEvent? found = null;
+        SendingEmailEvent? found = null;
 
         for (int i = 0; i < maxMessages; i++)
         {
@@ -171,7 +187,7 @@ public sealed class OutgoingEmailPublisherTests : IAsyncDisposable
             requeue.Add((result.DeliveryTag, result.Body.ToArray()));
 
             var json = Encoding.UTF8.GetString(result.Body.ToArray());
-            var evt = JsonSerializer.Deserialize<OutgoingEmailEvent>(json);
+            var evt = JsonSerializer.Deserialize<SendingEmailEvent>(json);
 
             if (evt?.Id == id)
             {