Kmail 1.3.1

I recently upgraded to KDE 2.2.1 and kdenetwork 2.2.1. Now I have Kmail 1.3.1. My problem is that now, with Kmail 1.3.1, I cannot send any mail. Every time I try to send a message I get an error message that says: "Response: 550 not local host xxx.com(or net), not a gateway" What's going on here? Thanks,