diff --git a/GreenArrow.Engine/Model/Events/DeliveryAttempt.cs b/GreenArrow.Engine/Model/Events/DeliveryAttempt.cs
index b782599..ad9e46b 100755
--- a/GreenArrow.Engine/Model/Events/DeliveryAttempt.cs
+++ b/GreenArrow.Engine/Model/Events/DeliveryAttempt.cs
@@ -88,7 +88,7 @@ public enum StatusEnum
         /// <summary>
         /// Primary key of the VirtualMTA that the message is assigned to.
         /// </summary>
-        public int Mtaid { get; init; }
+        public string Mtaid { get; init; }
 
         /// <summary>
         /// The time that the message was injected into GreenArrow’s queue, in seconds past the Unix epoch.
@@ -150,7 +150,7 @@ public enum StatusEnum
         /// Folded headers will simply contain the folding newlines/whitespace.
         /// As a header may be included in an email multiple times, the value of the JSON object is an array of strings.
         /// </summary>
-        public ICollection<string> Headers { get; init; }
+        public object Headers { get; init; }
 
         /// <summary>
         /// The size of the message (in bytes), if loaded from storage.
diff --git a/GreenArrow.Engine/Model/Events/EventType.cs b/GreenArrow.Engine/Model/Events/EventType.cs
index abf993f..d749edd 100755
--- a/GreenArrow.Engine/Model/Events/EventType.cs
+++ b/GreenArrow.Engine/Model/Events/EventType.cs
@@ -1,8 +1,13 @@
-namespace GreenArrow.Engine.Model.Events
+using Newtonsoft.Json;
+using Newtonsoft.Json.Converters;
+using Newtonsoft.Json.Serialization;
+
+namespace GreenArrow.Engine.Model.Events
 {
     /// <summary>
     /// Types of event generate by Green Arrow event processor
     /// </summary>
+    [JsonConverter(typeof(StringEnumConverter), typeof(SnakeCaseNamingStrategy))]
     public enum EventType
     {
         /// <summary>