diff --git a/src/Typesafe.Mailgun/FormPartsBuilder.cs b/src/Typesafe.Mailgun/FormPartsBuilder.cs
index 12bf9cd..89803bd 100644
--- a/src/Typesafe.Mailgun/FormPartsBuilder.cs
+++ b/src/Typesafe.Mailgun/FormPartsBuilder.cs
@@ -79,6 +79,15 @@ public static List<FormPart> Build(MailMessage message, IDictionary<string, IDic
 						result.Add(new SimpleFormPart("o:tag", tag));
 					}
 				}
+			}
+
+			if (message.Headers.AllKeys.Contains("X-Mailgun-Native-Send"))
+			{
+				var nativeSend = message.Headers.GetValues("X-Mailgun-Native-Send")?.FirstOrDefault();
+				if (nativeSend == "yes")
+				{
+					result.Add(new SimpleFormPart("o:native-send", "yes"));
+				}
 			}
 
 			result.AddRange(message.Attachments.Select(attachment => new AttachmentFormPart(attachment)));