Dev

.gitignore

@@ -416,3 +416,4 @@ FodyWeavers.xsd
 *.msix
 *.msm
 *.msp
+CLAUDE.md

Directory.Build.props

@@ -1,6 +1,13 @@
 <Project>
 
   <PropertyGroup>
+    <!-- Do not import the monorepo root Directory.Packages.props. This library owns its
+         own package versions and must also build correctly through local project references. -->
+    <ImportDirectoryPackagesProps>false</ImportDirectoryPackagesProps>
+    <!-- Opt out of Central Package Management — this library is a standalone
+         NuGet package with its own versioning, independent of the monorepo. -->
+    <ManagePackageVersionsCentrally>false</ManagePackageVersionsCentrally>
+
     <!-- Multi-targeting: .NET 8 (LTS), .NET 9, .NET 10 -->
     <TargetFrameworks>net8.0;net9.0;net10.0</TargetFrameworks>
 

README.md

@@ -81,12 +81,27 @@ await smtp2Go.Webhooks.DeleteAsync(webhookId);
 
 ### Receiving Webhook Callbacks
 
-SMTP2GO sends HTTP POST requests to your registered webhook URL when email events occur. The `WebhookCallbackPayload` model deserializes the inbound payload:
+SMTP2GO sends HTTP POST requests to your registered webhook URL when email events occur. Callbacks may arrive as JSON or as form-encoded payloads, and both should be normalized into the same `WebhookCallbackPayload` model:
 
 ```csharp
 [HttpPost("webhooks/smtp2go")]
-public IActionResult HandleWebhook([FromBody] WebhookCallbackPayload payload)
+public async Task<IActionResult> HandleWebhook(CancellationToken cancellationToken)
 {
+    WebhookCallbackPayload payload;
+
+    if (Request.HasFormContentType)
+    {
+        var form = await Request.ReadFormAsync(cancellationToken);
+        payload = WebhookCallbackPayloadParser.ParseFormValues(
+            form.SelectMany(pair => pair.Value.Select(value =>
+                new KeyValuePair<string, string?>(pair.Key, value))));
+    }
+    else
+    {
+        payload = await Request.ReadFromJsonAsync<WebhookCallbackPayload>(cancellationToken: cancellationToken)
+            ?? new WebhookCallbackPayload();
+    }
+
     switch (payload.Event)
     {
         case WebhookCallbackEvent.Delivered:

src/Smtp2Go.NET/Internal/Smtp2GoJsonDefaults.cs

@@ -11,6 +11,10 @@ namespace Smtp2Go.NET.Internal;
 ///     The SMTP2GO API uses snake_case naming convention for all JSON properties.
 ///     Null values are omitted from serialization to keep requests minimal.
 ///   </para>
+///   <para>
+///     Deserialization is case-insensitive because live webhook captures showed mixed casing for
+///     some callback keys (for example <c>Message-Id</c> and <c>Subject</c>).
+///   </para>
 /// </remarks>
 internal static class Smtp2GoJsonDefaults
 {
@@ -20,6 +24,7 @@ internal static class Smtp2GoJsonDefaults
   public static readonly JsonSerializerOptions Options = new()
   {
     PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
+    PropertyNameCaseInsensitive = true,
     DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull
   };
 }

src/Smtp2Go.NET/Models/Webhooks/BounceType.cs

@@ -73,21 +73,6 @@ public enum BounceType
 /// </remarks>
 public class BounceTypeJsonConverter : JsonConverter<BounceType>
 {
-  #region Constants & Statics
-
-  /// <summary>
-  ///   The SMTP2GO API string for hard bounces.
-  /// </summary>
-  private const string HardValue = "hard";
-
-  /// <summary>
-  ///   The SMTP2GO API string for soft bounces.
-  /// </summary>
-  private const string SoftValue = "soft";
-
-  #endregion
-
-
   #region Methods - Public
 
   /// <summary>
@@ -102,14 +87,7 @@ public override BounceType Read(
     Type typeToConvert,
     JsonSerializerOptions options)
   {
-    var value = reader.GetString();
-
-    return value switch
-    {
-      HardValue => BounceType.Hard,
-      SoftValue => BounceType.Soft,
-      _ => BounceType.Unknown
-    };
+    return WebhookCallbackValueParser.ParseBounceType(reader.GetString()) ?? BounceType.Unknown;
   }
 
   /// <summary>
@@ -123,14 +101,7 @@ public override void Write(
     BounceType value,
     JsonSerializerOptions options)
   {
-    var stringValue = value switch
-    {
-      BounceType.Hard => HardValue,
-      BounceType.Soft => SoftValue,
-      _ => "unknown"
-    };
-
-    writer.WriteStringValue(stringValue);
+    writer.WriteStringValue(WebhookCallbackValueParser.FormatBounceType(value));
   }
 
   #endregion

src/Smtp2Go.NET/Models/Webhooks/WebhookCallbackEvent.cs

@@ -116,32 +116,6 @@ public enum WebhookCallbackEvent
 /// </remarks>
 public class WebhookCallbackEventJsonConverter : JsonConverter<WebhookCallbackEvent>
 {
-  #region Constants & Statics
-
-  /// <summary>SMTP2GO callback payload string for the "processed" event.</summary>
-  private const string ProcessedValue = "processed";
-
-  /// <summary>SMTP2GO callback payload string for the "delivered" event.</summary>
-  private const string DeliveredValue = "delivered";
-
-  /// <summary>SMTP2GO callback payload string for the "bounce" event.</summary>
-  private const string BounceValue = "bounce";
-
-  /// <summary>SMTP2GO callback payload string for the "opened" event.</summary>
-  private const string OpenedValue = "opened";
-
-  /// <summary>SMTP2GO callback payload string for the "clicked" event.</summary>
-  private const string ClickedValue = "clicked";
-
-  /// <summary>SMTP2GO callback payload string for the "unsubscribed" event.</summary>
-  private const string UnsubscribedValue = "unsubscribed";
-
-  /// <summary>SMTP2GO callback payload string for the "spam_complaint" event.</summary>
-  private const string SpamComplaintValue = "spam_complaint";
-
-  #endregion
-
-
   #region Methods - Public
 
   /// <summary>
@@ -156,19 +130,7 @@ public override WebhookCallbackEvent Read(
     Type typeToConvert,
     JsonSerializerOptions options)
   {
-    var value = reader.GetString();
-
-    return value switch
-    {
-      ProcessedValue => WebhookCallbackEvent.Processed,
-      DeliveredValue => WebhookCallbackEvent.Delivered,
-      BounceValue => WebhookCallbackEvent.Bounce,
-      OpenedValue => WebhookCallbackEvent.Opened,
-      ClickedValue => WebhookCallbackEvent.Clicked,
-      UnsubscribedValue => WebhookCallbackEvent.Unsubscribed,
-      SpamComplaintValue => WebhookCallbackEvent.SpamComplaint,
-      _ => WebhookCallbackEvent.Unknown
-    };
+    return WebhookCallbackValueParser.ParseCallbackEvent(reader.GetString());
   }
 
   /// <summary>
@@ -182,19 +144,7 @@ public override void Write(
     WebhookCallbackEvent value,
     JsonSerializerOptions options)
   {
-    var stringValue = value switch
-    {
-      WebhookCallbackEvent.Processed => ProcessedValue,
-      WebhookCallbackEvent.Delivered => DeliveredValue,
-      WebhookCallbackEvent.Bounce => BounceValue,
-      WebhookCallbackEvent.Opened => OpenedValue,
-      WebhookCallbackEvent.Clicked => ClickedValue,
-      WebhookCallbackEvent.Unsubscribed => UnsubscribedValue,
-      WebhookCallbackEvent.SpamComplaint => SpamComplaintValue,
-      _ => "unknown"
-    };
-
-    writer.WriteStringValue(stringValue);
+    writer.WriteStringValue(WebhookCallbackValueParser.FormatCallbackEvent(value));
   }
 
   #endregion

src/Smtp2Go.NET/Models/Webhooks/WebhookCallbackPayload.cs

@@ -8,25 +8,46 @@ namespace Smtp2Go.NET.Models.Webhooks;
 /// <remarks>
 ///   <para>
 ///     SMTP2GO sends HTTP POST requests to registered webhook URLs when email
-///     events occur. This model deserializes the inbound webhook payload.
+///     events occur. This model is the canonical in-memory representation of
+///     JSON and form-encoded webhook callbacks.
 ///   </para>
 ///   <para>
-///     The fields populated depend on the event type:
+///     Live callbacks captured in the integration test suite showed that SMTP2GO does not emit one
+///     stable callback shape. The fields populated depend on the event type:
 ///     <list type="bullet">
 ///       <item><see cref="Recipient"/> (<c>rcpt</c>) is present for delivered and bounce events.</item>
 ///       <item><see cref="Recipients"/> is present for processed events (array of all recipients).</item>
 ///       <item><see cref="BounceType"/>, <see cref="BounceContext"/>, and <see cref="Host"/>
 ///             are present for bounce and delivered events.</item>
 ///       <item><see cref="ClickUrl"/> and <see cref="Link"/> are only present for click events.</item>
+///       <item>
+///         Processed and delivered callbacks include additional provider metadata such as
+///         <c>id</c>, <c>auth</c>, <c>message-id</c>/<c>Message-Id</c>, <c>subject</c>/<c>Subject</c>,
+///         <c>from</c>, <c>from_address</c>, and <c>from_name</c>.
+///       </item>
 ///     </list>
 ///   </para>
 /// </remarks>
 /// <example>
 ///   <code>
 ///     // In an ASP.NET Core controller:
 ///     [HttpPost("webhooks/smtp2go")]
-///     public IActionResult HandleWebhook([FromBody] WebhookCallbackPayload payload)
+///     public async Task&lt;IActionResult&gt; HandleWebhook(CancellationToken cancellationToken)
 ///     {
+///       WebhookCallbackPayload payload;
+///
+///       if (Request.HasFormContentType)
+///       {
+///         var form = await Request.ReadFormAsync(cancellationToken);
+///         payload = WebhookCallbackPayloadParser.ParseFormValues(
+///           form.SelectMany(pair => pair.Value.Select(value => new KeyValuePair&lt;string, string?&gt;(pair.Key, value))));
+///       }
+///       else
+///       {
+///         payload = await Request.ReadFromJsonAsync&lt;WebhookCallbackPayload&gt;(cancellationToken: cancellationToken)
+///           ?? new WebhookCallbackPayload();
+///       }
+///
 ///       switch (payload.Event)
 ///       {
 ///         case WebhookCallbackEvent.Delivered:
@@ -64,6 +85,22 @@ public class WebhookCallbackPayload
   [JsonPropertyName("email_id")]
   public string? EmailId { get; init; }
 
+  /// <summary>
+  ///   Gets the SMTP message identifier observed in the webhook callback.
+  /// </summary>
+  /// <remarks>
+  ///   <para>
+  ///     This is distinct from <see cref="EmailId" />. <see cref="EmailId" /> is SMTP2GO's provider-side
+  ///     correlation ID returned by the send API, while this property carries the RFC 5322 Message-ID style
+  ///     value observed in webhook callbacks.
+  ///   </para>
+  ///   <para>
+  ///     Live callbacks emitted this field with inconsistent casing (<c>Message-Id</c> and <c>message-id</c>).
+  ///   </para>
+  /// </remarks>
+  [JsonPropertyName("message-id")]
+  public string? MessageId { get; init; }
+
   /// <summary>
   ///   Gets the type of event that triggered this webhook callback.
   /// </summary>
@@ -97,6 +134,35 @@ public class WebhookCallbackPayload
   [JsonPropertyName("sendtime")]
   public DateTimeOffset? SendTime { get; init; }
 
+  /// <summary>
+  ///   Gets the message subject observed in the webhook callback.
+  /// </summary>
+  /// <remarks>
+  ///   Live callbacks emitted this field with inconsistent casing (<c>Subject</c> and <c>subject</c>).
+  /// </remarks>
+  [JsonPropertyName("subject")]
+  public string? Subject { get; init; }
+
+  /// <summary>
+  ///   Gets the provider-specific callback event identifier.
+  /// </summary>
+  /// <remarks>
+  ///   This maps to the raw <c>id</c> field observed in live callbacks. Different events for the same
+  ///   <see cref="EmailId" /> can carry different values, so this is treated as an event-level identifier.
+  /// </remarks>
+  [JsonPropertyName("id")]
+  public string? EventId { get; init; }
+
+  /// <summary>
+  ///   Gets the opaque provider auth marker observed in live callbacks.
+  /// </summary>
+  /// <remarks>
+  ///   The exact semantics are undocumented. Live callbacks included values such as a truncated API key
+  ///   prefix, so the library preserves the field as opaque diagnostic metadata.
+  /// </remarks>
+  [JsonPropertyName("auth")]
+  public string? Auth { get; init; }
+
   /// <summary>
   ///   Gets the per-event recipient email address.
   /// </summary>
@@ -116,6 +182,29 @@ public class WebhookCallbackPayload
   [JsonPropertyName("sender")]
   public string? Sender { get; init; }
 
+  /// <summary>
+  ///   Gets the raw <c>from</c> field observed in live callbacks.
+  /// </summary>
+  /// <remarks>
+  ///   Live callbacks included <c>sender</c>, <c>from</c>, and <c>from_address</c>. They carried the same
+  ///   address in the captured delivered and processed payloads, so this property is preserved separately
+  ///   to avoid losing transport detail.
+  /// </remarks>
+  [JsonPropertyName("from")]
+  public string? From { get; init; }
+
+  /// <summary>
+  ///   Gets the raw <c>from_address</c> field observed in live callbacks.
+  /// </summary>
+  [JsonPropertyName("from_address")]
+  public string? FromAddress { get; init; }
+
+  /// <summary>
+  ///   Gets the raw <c>from_name</c> field observed in live callbacks.
+  /// </summary>
+  [JsonPropertyName("from_name")]
+  public string? FromName { get; init; }
+
   /// <summary>
   ///   Gets the list of all recipients of the original email.
   /// </summary>