APPLE IPhone trouble with ATT

AndyV Says: 
November 17th, 2008 at 1:07 pmHere’s the scoop:
Apple decided it was better to preserve iPhone battery charge by checking mail only when a user wakes the iPhone up or a “network event” wakes it up (e.g. changing cells towers).
There is a known bug in Apple’s POP3 Fetch where the iPhone doesn’t close the POP3 session properly on the mail server. This leaves the session open until the server session times out. POP3 does not allow more than one session, so until it times out the iPhone (or any desktop or laptop client trying to access the same mailbox) cannot connect to that same mailbox.

you can try syncing the mail account into phone from entourage using itunes. The mail application in the iphone can be a pain to set up using other email providers, rather than gmail, yahoo, aol, .mac, which are actively supported on the iphone and set up without a hitch. Make sure this account you are trying to add to the iphone supports imap, multiple client usage. Check for any alternative hostnames for the email client, delete email account from phone, re-add it.