Cannot send message using the server

I can receive mail but not send it with my local account through Apple Mail. It is a POP account and whenever I try to send an email through it from Apple Mail, I get the error, "Cannot send message using the server smtp-server.triad.rr.com" and it asks me to pick a different outgoing mail server. My other server is my North Carolina State University account which I can only get to work on campus. I have talked to my ISP and all of the server addresses seem to be correct as well as the port and authentication settings. The only thing we could think of is that I recently installed Norton Symantec Antivirus as required by my school. It is possible that it is blocking the sent email because the admin has not given me the privileges to see or change any preferences. I tried deleting it and the error persists after restarting. The web client works so it does not seem to be a server side problem. This has been quite aggravating, can anyone please help me?

Thanks,
Dreier Carr