Yes there is. on the iPhone, tap Settings >> Mail, Contacts, Calendars >> Tap your email account >> Tap SMTP…… Under secondary servers there is one that says AT&T SMTP Server. Tap this and turn it on.

Make sure that you are not connected to Wi-Fi and you should be able to send out mail now.

If not, remove the account and add it again.

no such thing as SMTP for hotmail since its a free service.
just remove the account and do it again.