basic mail

[Eric]

THis is a lob, I guess, but here goes: 
Let's say that I try to send a message in mutt, but do so before I 
have properly configured sendmail.  The failure to properly 
configure it causes my messages to look like they are coming 
<my_computer_name@localdomain>.  Sendmail doesn't like this, so 4 hours later
it sends me a warning stating that it was unable to send my message because
it did not like my address, but that it will try later to send the same 
message.

What I want to do is go find that message and prevent sendmail from sending it.
Where is that message; i.e., how do I find it so I can delete it and 
prevent sendmail from sending it?

Thanks, 

Eric