Opt-out lists in AWS End User Messaging SMS

An opt-out list is list of destination phone numbers that should not have messages sent to them. When you send SMS messages, destination identities are automatically added to the opt-out list if they reply to your originator phone number with the keyword STOP (unless you enable the self-managed opt-out option). If you attempt to send a message to a destination number that is on an opt-out list, and the opt-out list is associated with the phone number used to send the message, AWS End User Messaging SMS doesn't attempt to send the message.

By default, opt-outs are managed by AWS automatically. You can choose to disable this automatic opt-out handling by enabling self-managed opt-outs. Your account can contain both numbers for which opt-outs are managed by AWS, and numbers for which you manage opt-outs yourself.