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SMS Opt-Out Keywords and Stop Words
SMS Opt-Out Keywords and Stop Words
Learn more about how Telnyx processes SMS opt-outs and handles stop words
Telnyx Engineering avatar
Written by Telnyx Engineering
Updated over a week ago

What are SMS Opt-Out Keywords?

Telnyx automatically processes incoming messages and recognizes English-language stop words. Stop words are specific words such as STOP or UNSUBSCRIBE that signal that a person no longer wishes to receive messages from you.

When Telnyx identifies a stop word, the person's phone number is added to the opt-out list and you will no longer be able to send messages to that number. Any further messages from your account that are sent to a number on the opt-out list will not be processed.

Coming soon: You will soon be able to retrieve all phone numbers that are on the opt-out list.

Telnyx recognizes the following English-language stop words:

  • stop

  • stopall

  • stop all

  • unsubscribe

  • cancel

  • end

  • quit

Please note that stop words are only recognized if they are the only words in the message. For example, "stop all" is recognized but "please stop all messages" would not be recognized.

To restart messages the number that opted out has to send any of the following opt-in keywords to the exact same number they opted out from:

  • start

  • unstop

Number pool

Note that to be able to restart messages, the end user needs to send the opt in keywords above to the exact same number they opted out from. When using our number pool feature you might not get clarity as what number they opted out from since it you used several numbers to send messages out. You should be able to find the opt out SMS in your MDRs by filtering for number that opted out, this way you can easily determine the number where the opt in needs to be sent to.

Who handles the auto response from an opt out?

By default, Telnyx will handle the auto response. If a user of your services decides to opt out via one of the above stop words towards your numbers, Telnyx will detect this and automatically send out a generic unsubscribed message from the number that received the opt out message.

Generic Messages:

  • "You have successfully been unsubscribed, you will not receive any more messages from this number. Reply START to re-subscribe."

  • You have successfully been re-subscribed to this number. Reply STOP to unsubscribe. Msg&Data Rates May Apply.

However, It is possible to allow for custom block rules and auto responses on a per messaging profile basis but recommend contacting our sales team ( to discuss this further.

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