How is opt-out managed when sending SMS from a US Toll free number?


What happens when a user sends stop to my toll free number?

Can a user re-subscribe once he/she sent stop?


The Opt-out flow for US toll free numbers is mandated by the US carriers and it is as follows:

  • A user sends the word 'STOP' to the toll free number.
  • The carrier sends the following outbound message to the user: 'NETWORK MSG: You replied with the word "stop" which blocks all texts sent from this number. Text back "unstop" to receive messages again.'
  • Any subsequent MT messages sent from the toll free number will fail with error code 9 - 'Illegal Number - you tried to send a message to a blacklisted phone number. That is, the user has already sent a STOP opt-out message and no longer wishes to receive messages from you.'
  • If the customer wishes to re-subscribe to the service, he/she can send a new message to the Toll Free number with the word 'UNSTOP'.
  • User 'STOP' and 'UNSTOP' requests are forwarded back to customers.
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