SMS carriers worldwide support automatic functions for end-users based on specific keywords. 

The keywords and functions are managed at the carrier level and are permanently active.  

Opt-out keywords

The following keywords automatically block the number sending the keyword from receiving further messages from the number to which the keyword is sent.

• STOP
• CANCEL
• END
• OPTOUT
• OPT-OUT
• QUIT
• UNSUBSCRIBE

Carrier keywords are non-case-sensitive. 

Only the keyword by itself will trigger the phone number block.  For example, replying "STOP" or "Cancel" will stop the contact from receiving messages from that specific phone number, but replying "Please Stop" or "CANCEL PLEASE" will not.

Opt-out keywords will function regardless of whether the message being replied to includes instructions for using them (e.g. the "Reply STOP to stop" suffix).

Replying to this confirmation message with a carrier opt-in keyword will undo the block, as the carriers send it 'from' the number to the end-user handset.

Confirmation messages

The carrier will send one of the following messages to the end user confirming the opt-out, depending on the outbound and/or inbound number. 

These messages are sent directly from the carrier.  There is no charge, and they do not appear in Sakari messaging reports.

Example Default Reply #1

NETWORK MSG: You replied with the word "stop", which blocks all texts sent from this number. Text back "unstop" to receive messages again.

Example Default Reply #2

[Brand]: You have successfully been unsubscribed. You will not receive any more messages from this number. Reply START to resume.

Sakari support

When an opt-out keyword is received by a number dedicated to a Sakari account, the contact record related to the number from which the keyword is received is blocked.

All subsequent message attempts will not be sent to the carrier, and the message will display an error in Sakari.

This avoids carrier charges for an attempt to send a message to a number opted-out by keyword.