I think this is the same issue. When my OS 10.4 Mail client receives an attachment generated in a group mailing from an XP workstation sent via Outlook through our intranet Exchange server, the attachment, usually an MS Office document, arrives corrupt, labeled 'mime-attachment' and unable to be opened whether or not I append the proper extension. I have tried looking at the code to determine if I can identify the resource fork, etc but no luck. The other curiosity is that URL's arrive duplicated. Our IT department does not support Maill.app so will not fix the problem at its origin. I cannot use our Exchange server because of attachment restrictions, so I maintain a POP account on one of our Unix servers. Again, this only arises with group mailings, never an individual message from anyone on any platform.