To email an AT&T phone, follow these steps:
1) Open your email client on your cell phone or laptop and compose a message.
2) In the "To" box, enter [recipient's 10 digit cell phone number]@txt.att.net. For example, firstname.lastname@example.org. If you're sending multimedia files (MMS), use [recipient's 10 digit cell phone number]@mms.att.net.
3) Press send! The recipient should receive the email message shortly.
4) Follow these handy tips for emailing cell phones!