UPDATED: Better validation before creating a duplicated TicketCC

helpdesk/management/commands/get_email.py

@@ -198,7 +198,9 @@ def create_object_from_email_message(message, ticket_id, payload, files, quiet):
 
     if in_reply_to is not None:
         try:
-            previous_followup = FollowUp.objects.get(message_id=in_reply_to)
+            queryset = FollowUp.objects.filter(message_id=in_reply_to).order_by('-date')
+            if queryset.count() > 0:
+                previous_followup = queryset.first()
                 ticket = previous_followup.ticket
         except FollowUp.DoesNotExist:
             pass #play along. The header may be wrong

helpdesk/views/staff.py

@@ -348,7 +348,7 @@ def subscribe_to_ticket_updates(ticket, user=None, email=None, can_view=True, ca
     }
 
     ticket_cc_form = TicketCCForm(data)
-    if ticket_cc_form.is_valid():
+    if ticket is not None and ticket_cc_form.is_valid():
 
         queryset = TicketCC.objects.filter(ticket=ticket, user=user, email=email)