Can receive mail but can't send it out. What the heck?

I recently had some trouble with my mail (along with all my photos) but I called my ISP, talked to a very nice Mac lady at tech support (how about that, huh?) and got Mail working fine. Basically, Mail had deleted my wavecable account and gone back to my .Mac account which I had for about 30 minutes last summer. With the lady's help, I re-enturned the wavecable info and everything seemed good. I got all my backlogged e-mails and the Web's looking fine! Great joy!
However, the next time I tried to send an e-mail out, no such luck. (It was a few days later.) All I get is a message saying:
"Cannot send message using the server mail.wavecable.com
Use the pop-up menu below to try a different outgoing mail server.
All messages will use this server until you quit Mail or change your
network settings.
Message from brian hardy <hardyfamily@wavecable.com>"
And then it gives me the "Send message using: smtp.mac.com.hardyfamily1" dropdown menu.
The 3 buttons at the bottom are "edit message", "Use Selected Server" and "Try Again Later".

Well, the .Mac account is long expired so I can't use it. I've tooled around Mail's perferences and it sure looks like I should be able to use wavecable. Can any of you specify exactly where I should be able to change this?
Thanks.


800Mhz eMac. Superdrive. 60Gig HD Mac OS X (10.4.4) Mail 2.0.5