STOP is default keyword in Mobile Connect - you don't need to implement it and you are not able to disable the functionality. You can read more about them here.
To be able to respond or opt-out the customer needs to know the long code (sender mobile number) that was used by your communication. If this number is available and the customer successfully sends to your sender number, she/he will be fully opted-out from communication from this number (the subscription status on all keywords will be set to "not opted in").
In the payload that is used to send SMS, you have three important values related to the subscription status:
- keyword (required when
There are a few cases that are possible:
"Subscribe": "false" - only send to contacts that already exist in Mobile Connect
"Subscribe": "true" - create a mobile subscription if the customer does not exist (you need to then add the
"keyword" value). The "not opted in" status will be respected and the text message won't be delivered
"Subscribe": "true", "Resubscribe": "true" - This creates the customer in Mobile connect where not available already and should change the subscription status, but this does not work when I tested it (the status stays opted-out)
In your case I would recommend using
"Subscribe": "true" without the resubscibe parameter.