STOP receiving SMSes when using Twilio with C#.net

Question

I am sending SMS via twilio C# to selected phone numbers. I see in FAQs in twilio that it is possible to filter out the numbers who do not wish to receive SMSes. I see this

Answer 1

My understanding is that twilio 'intercepts' the SMS message, recognizes the 'STOP', does what processing it needs to to suppresses future SMS messages on their end, but the original message will still get passed to you as always, so you will have the ability to still handle it on you end as well.

Answer 2

Twilio Evangelist here.

This is a great question: for normal numbers when the persons sends back a 'STOP' message, Twilio will prevent your account from sending an SMS to that person again. However we will also log the 'STOP' message to your SMS logs so that you know they have opted out.

The person sending the 'STOP' SMS will then get this message

"You have successfully been unsubscribed You will not receive any more messages from this number. Reply START to resubscribe."

If you attempt to send them an SMS again, you will get an error from the REST API: "21610: Message cannot be sent to the 'To' number because the customer has replied with STOP".

The person can opt back into your messages by sending a 'START' message.

Hope this helps.