add send error handling

src/MailKitMailModule.cs

@@ -240,6 +240,8 @@ namespace OpenSim.Modules.EMail
         }
 
         public void SendEmail(UUID objectID, string address, string subject, string body)
+        {
+            try
             {
                 SceneObjectPart sceneObject = m_scene.GetSceneObjectPart(objectID);
 
@@ -277,6 +279,11 @@ namespace OpenSim.Modules.EMail
                     client.Send(message);
                     client.Disconnect(true);
                 }
+            }catch(Exception _error)
+            {
+                m_log.Error("[" + Name + "] " + _error.Message);
+            }
+
         }
 
         public Email GetNextEmail(UUID objectID, string sender, string subject)