The information contained in the BellSouth welcome email is wrong. It has been wrong for years yet they continue to send it to millions of customers. The email server names are wrong and DNS could be wrong (or at least different from what you are being assigned).

The BellSouth POP and SMTP email server address is mail.bellsouth.net.
In the past, the server address contained a three letter city code (i.e. mail.atl.bellsouth.net or mail.mia.bellsouth.net etc.). This code was dropped in mid 2001. For more information see the BellSouth Email Configuration Site or the FAQ here.

The DNS addresses contained in the email may also be wrong. First off, unless you are very familiar with DNS do not hard code your DNS. DNS is automatically assigned by BellSouth and can change due to load or network issues. If you are familiar with DNS and need alternate BellSouth DNS IP addresses check here.

Hopefully someday BellSouth will fix this, as it is pretty embarrassing.