Originally Posted by voda_black
Good point. Will raise with AV Company and see if there is a solution...
Yeah that is a top point actually. We have had to advise lots of customers who use 3rd party services to disable this change due to our in house anti-spam systems rejecting the mail. IMHO 3rd party mail-handling services shouldn't be altering the header unless you asked them to, you should get the email as intended.