The AT&T Short Code and 10-Digit A2P SMS Messages Code of Conduct governs the existing Short Code Application-to-Person (A2P) messaging system and the AT&T 10-digit long code (10DLC) A2P Messages. The 10DLC A2P Messages allows A2P SMS traffic originating from 10DLCs outside of AT&T’s network to be delivered to AT&T mobile customers.