[fetchmail]invalid domain -- deleted

Hello,

    I am running Fetchmail installed from the ports collection on FreeBSD 4.3 
with Postfix into uw-imap
Fetchmail works great, 
Except I don't want it to delete email when the sender has an invalid domain 
name. (Error 501) 
I work in a tech support center and customers email us for support and at times 
they miss type their return address.

Is there something I could type into .fetchmailrc to prevent fetchmail from 
doing this.

Thank you for the support and fetchmail.
Jason