AT&T is reportedly sending out a free text message to iPhone subscribers, notifying them of the imminent activation of MMS service on September 25th. The text additionally warns that the "View My Message" option will be disabled while accounts are readied, but that sending and receiving text messages should remain possible. Only the iPhone 3G and 3GS will be able to send MMS content.

User anecdotes suggest that AT&T has already been gradually activating MMS, potentially to test for weaknesses in network traffic and implementation. MMS may add significantly to AT&T's bandwidth problems in some areas, namely New York City and San Francisco, where the carrier is already unable to cope with heavy iPhone data traffic. MMS allows users to exchange photos and video without using e-mail or direct transfers, including to people without smartphones.