Is it possible for users to opt-in and out of different topics and receive messages only on topics they have opted in for?
Yes, it is possiblefor users to opt-in to different topics. You must send out a one-time notification request, according to the official guide from Facebook.
Through our system, you can automatically tag the users with topics they have opted in for and send out custom messages to a specific target group of members. However, you may need to request the user to continue subscribing to notifications after each push message.
Please click here to set up one-time notification on Stella.