New 21.5-inch Retina 4K models expected.
AT&T Activates MMS Functionality for U.S. iPhone Users
Apple has posted a support article outlining the process for activating MMS, which involves updating a carrier settings file on users' iPhones via iTunes. Users are prompted to connect their iPhone to iTunes and click the "Check for Update" button. Users should update to iPhone OS 3.1 if they have not already done so, and then click the "Update Settings" button on the pop-up window notifying them that a new carrier settings file is available.
After installation of the new carrier settings file, users must restart their devices. Apple recommends that users verify that the functionality is active by creating a new text message. A camera icon should be available.