Learned this today (7/31/2012). AT&T has changed the names of the POP and SMTP servers for all email accounts for att.net, sbcglobal.net, and several others (a list is below). Some users will immediately find that Outlook or other email software will not send or receive email, until it is reconfigured to match; it is not unlikely that the changes will not affect everyone at once, but will eventually become essential.

Previously, each of the domains below had different server names for sending and receiving; now, they are all the same, inbound.att.net for reception (POP) and outbound.att.net for transmission (SMTP). POP has to be done on port 995, SSL turned on; SMTP has to be done on port 465, also with SSL turned on.

ameritech.net
att.net
bellsouth.net
flash.net
nvbell.net
pacbell.net
prodigy.net
sbcglobal.net
snet.net
swbell.net
wans.net