Attachment issue over smtp

HiI have recently upgraded from 5.12 to 6.5.3 (servers and clients). All clients are set to notes rich text format. I’ve configured the domino smtp server to handle the mine conversions. However since the update some emails sent over the internet are having the attachments stripped. Also the text with the body is also arriving as an attachment!. This only happens to a few internet domains. They worked fine previous to the upgrade

any ideas??

Subject: Attachment issue over smtp

Edit person doc and change Format preference for incoming mail to “keep in senders’ format”.