AT&T Outgoing Mail Servers?

I have two email accounts that do not allow me to send from my iPhone as they cannot connect to the outgoing mail servers I have specified. I remember when I was a Blackberry user with Verizon having to obtain a login and utilize Verizon's outgoing mail servers. Is this the case with AT&T as well? Usually its because ISP's firewalls block access to certain things as they'd prefer you to use theirs.

Thanks for your advice!

who are the mail accounts through?

Well one was Gmail and the other is a web hosting domain through GoDaddy. I got it figured out though, just took the right combination. The Gmail was a simple delete and readd, the GoDaddy account was more difficult.

Thanks!