Creates a new opt-out list.

If the opt-out list name already exists, an error is returned.

An opt-out list is a list of phone numbers that are opted out, meaning you can't send SMS or voice messages to them. If end user replies with the keyword "STOP," an entry for the phone number is added to the opt-out list. In addition to STOP, your recipients can use any supported opt-out keyword, such as CANCEL or OPTOUT. For a list of supported opt-out keywords, see SMS opt out in the End User Messaging SMS User Guide.