http://bugs.winehq.org/show_bug.cgi?id=11770
--- Comment #14 from Austin English austinenglish@gmail.com 2009-11-11 21:03:25 --- (In reply to comment #13)
(In reply to comment #12)
Owen recently did a lot of work on this: http://source.winehq.org/git/wine.git/?a=history;f=dlls/mapi32;hb=HEAD
I think this may be fixed now.
It should be fixed for Windows-based mail clients, but native clients will still not support attachments.
Using xdg-mail?