Opt Out is a commonly used phrase meaning that a recipient has indicated that they no longer wish to receive messages from a sender. Regardless of how the recipient originally got on the list, if they opt out then they should be immediately removed from any list or address book and cease to be sent any further messages.
The normal method of opting out is for recipient to reply to a SMS message with STOP or REMOVE. However, if they use any other term, phrase or language to indicate they no longer want to receive messages then failure to abide by that request may result in loss of service. We suggest you add Stop SMS? Reply with STOP to each of your messages.
Bulletin Connect manages this process for clients by scanning incoming messages for those with the phrase stop in them, and adds the MSISDN to a list of blocked numbers. The client account can not send to these numbers again until they are removed from this list.
Also see: SDK for more information on the Bulletin Connect Opt-Out process.