SUPPORT.TWILIO.COM END OF LIFE NOTICE: This site,, is scheduled to go End of Life on February 27, 2024. All Twilio Support content has been migrated to, where you can continue to find helpful Support articles, API docs, and Twilio blog content, and escalate your issues to our Support team. We encourage you to update your bookmarks and begin using the new site today for all your Twilio Support needs.

Error 21610 "The message From/To pair violates..." when sending SMS

The Twilio API will return this message if you attempt to send an SMS or MMS to a recipient who has previously replied to your Twilio number with one of the following keywords:

  • STOP
  • END
  • QUIT

In this scenario, your message would not be sent, and you would not be charged for the message attempt.

Notice: When a user opts out of a phone number that belongs to a Messaging Service, the user is also opted out to receiving all messages sent from that particular Messaging Service.

In order to successfully send messages to such recipients, they must opt in to your messages by texting your number with one of the following keywords:

  • YES

Additional resources

Have more questions? Submit a request
Powered by Zendesk