I want to set up multiple email aliases to use with the inbuilt mail client.

I.e. I want to check incoming IMAP4 mail in one account only and be able to select XXX@XXX.com or XX2@XX2.com etc as the identity when sending mail, they are all sent from the same SMTP server.

Can this be done, I can't figure out how, i.e. I would have to setup a new account, but then this will also check mail, and it will thus check mail twice in the same location.

Can multiple sending aliases be accomplished with the inbuilt client?