Change a pool's opt-out list 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 origination 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 pool used to send the message, AWS End User Messaging SMS doesn't attempt to send the message.
By default, when a pool is created it is assigned to the Default opt-out list. Pools can share the same opt-out list. When you change a pools opt-out list any recipients who previously opt-out might not be in the new list and start to receive messages. For more information on adding or removing destination phone numbers from an opt-out list, see Add a destination phone number to an opt-out list in AWS End User Messaging SMS.