newbie question; how to define an outbox

[Stefan Antoni]

I am a one-week-newbie in using mutt and i want to
save my outgoing mail in an outbox like i can do
it with KMail and other known email-clients.

How do i create such an outbox and tell mutt to dump
outgoing mail automatically into it.

finally, i'd like to have something like that in my
/home/myname :

mbox.in  <-- already created for incomming mail.
mbox.out <-- the mailbox for outgoing mail.

-- 

thx in advance,
Stefan Antoni