I'm got an exchange box with 5 aliases currently loaded up. It recieves mail fine, however I want to be able to send mail out using the aliases too - so I don't have to reveal my primary mail address. 

Is it possible to change it without having to change the mail address everytime in the Account perferences? 

I had a better system working with Apple mail (having seperate mailboxes) however... there was a problem with pocket pcs supporting IMAP properly so I've had to go to an exchange solution. 

Any ideas?