[MlMt] send messages from one account and save in Sent folder of another account

[Aram Harrow]

I am looking for analogue of gmail "send mail as".

When I use the web gmail client I use the "send mail as" feature to send 
emails from my work email address, and gmail automatically places them 
in the gmail Sent mail folder.  When I do this from mailmate, gmail is 
not used at all so the message does not appear in my gmail Sent folder; 
instead it goes to my work Sent mail folder.
Does anyone know how to  set up mailmate to send mail using the mit.edu 
IMAP server but saving the message in the gmail.com Sent mail folder?
Thanks, and apologies if this question has been asked before.

-aram