Opt-Out to Text Messaging
The first time you send a message to a consumer, a STOP message is appended to the end of the message. The STOP message will only send to a phone number one time. The message appended will say "Text STOP to opt out"
Other opt-out keywords that consumers can text are STOP, STOPALL, UNSUBSCRIBE, CANCEL, END, QUIT and REMOVE. None of these keywords are case sensitive. They are also not included in the original STOP message that appears the first time your send a message, but they will still work.
If a consumers expresses they want to opt out, but doesn't actually text any of the opt out keywords above, you can suppress them to ensure you don't accidently message them again.
Opt-In to Text Messaging
The only way an opted-out contact can receive your messages again is to text in an opt-in keyword. The opt-in keywords are START, YES and UNSTOP.