unsent mail folder

[Victor]

When I send mail it turns out to be sent even though I'm not connected to my ISP. In 
fact, I see the unsent messages in the sent-mail folder. 

How could I tell mutt to put these queued, unsent messages in a folder (like 
'unsent-mail' or 'queued-mail') and have them automatically moved to 'sent-mail' 
folder when they've actually been sent?

Ciao
Vittorio