I cannot access to sbcglobal email address from iphone.

All of the sudden, I am unable to access to my sbcglobal email address from my iPhone. I tried from my laptop and it works. I tried from Safari on my iPhone and it works, but cannot access, send or receive emails from "Email" setting on my iPhone. I deleted the account and added the same account, but now all the folders are gone and cannot send or receive any emails. I'm using Incoming mail server "imap.mail.att.net", saved my email address and password. Outgoing mail server "smtp.mail.att.net", saved my email address, password, use SSL, Authentication with "password" and Server port 465 (and also tried 587), but no luck. I noticed that when I entered my email address and password for Outgoing mail server, the error message says "The mail server "smtp.mail.att.net" is not responding. Verify that you have entered the correct account info in Mail settings." I entered all the correct information. Please help!!