Twilio, by default, handles standard English-language reply messages such as STOP, BLOCK or CANCEL for long code messages for you in accordance with industry standards. Supported opt-out and opt-in keywords on long code messaging are listed below:
- STOP, STOPALL, UNSUBSCRIBE, CANCEL, END, and QUIT - will stop customers from receiving messages from that particular Twilio number. When attempting to send a message to a subscriber that previously texted in any of the keywords mentioned above, Twilio's API will throw a 400 response with error code 21610. If you are using more than one long code, customers who text STOP, STOPALL, UNSUBSCRIBE, CANCEL, END or QUIT to one of your long codes will not be prevented from receiving messages sent from other of your long codes unless you take additional action separate from Twilio to prevent that from occurring. In addition, only single-word messages will trigger the block. So, for example, replying “STOP” will stop the customer from receiving messages from that particular Twilio number, but replying “STOP PLEASE” will not. Further, the block works and is logged even if your number currently has no messaging request URL.
- START, YES and UNSTOP will opt customers back in to the messages coming from your Twilio phone number, and these messages will also be delivered to your Twilio account as well as the defined web hook so you can update your application logic.
- HELP and INFO will return a message informing the customer that they can use the above commands to control the delivery of messages. Twilio does not send such messages to your web hook.
It is currently not possible to customize the default response triggered by these keywords.
Note:Text message campaigns may be subject to various legal compliance requirements depending on the nature of your text messaging campaign, the location from where you are sending your text messages, and the location of your recipients. While Twilio will handle the above-described messages on long codes in the way described in this article, you should consult with your legal counsel to ensure that your text messaging campaign conforms will need to meet all applicable legal compliance requirements.
STOP Filtering for Short Codes
Twilio does not handle default STOP filtering for short codes. For information on short code HELP and STOP responses, please see this article.
STOP Filtering and Opt-out Mechanism with Messaging Services
Twilio's opt-out mechanism with Messaging Services is stricter due to the shared "Number Pool" concept.
When a user texts "STOP" or other keywords to opt out of a phone number that belongs to a Messaging Service, the user will also be opted out of receiving messages sent from all phone numbers associated with that particular Messaging Service.
If you have further questions on this, please contact Twilio Support.