How to save outgoing mail

Hi,

I'm running exim on FC 5. Is there anyway to
save all outgoing mail (sent from Thunderbird, etc.)
to the corresponding user's "Sent" folder on the
server?

Basically, it's like when I check the "Leave messages
on server" in my e-mail client's preferences. That leaves
a copy of received mail on the server. Is there
an equivalent for saving sent mail on the server?

Thanks in advance,

-Jason