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# What happens when a user sends STOP to my toll-free number? (U.S. only)

**Applies To**
Toll-Free Numbers
Outbound SMS
Opt-Out
US Carriers

**Answer**
The opt-out flow for US toll-free numbers is mandated by US carriers and 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 and the message 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 user wishes to re-subscribe to the service, they can send a new message to the toll-free number with the word UNSTOP.
* User STOP and UNSTOP requests are forwarded back to users.