[MlMt] how to best configure MM/Gmail to handle Gmail "Send mail as"

[Paula Coelho]

hi there,

here is the thing, i've got two work emails addresses, but their server 
is very limited in space, so I forward everything to a Gmail account 
now. I've added both work addresses in Gmail in "Send mail as" with the 
"Not an alias" option.

when i read emails in MM, it does see it was send to the work address 
and hitting reply works correctly putting the work email as sender. but 
then the sent email is stored in the work IMAP server, and i loose the 
thread abilities for that exchange.

bottom line: how can I make MM send an email with the sender being the 
work address, but storing the message in Gmail server instead of the 
work server?

thx
paula