Star Messages. Premium subscribers can set a fee for incoming messages from users outside their contacts – to reduce spam or monetize their inbox.

By default, your contacts and people you've contacted first can message you freely. Star messages support granular exceptions for other users or entire groups.

Star messages can also be enabled in group chats and channel discussions.

To enable Star messages for your private chats, go to Settings > Privacy and Security > Messages. For groups, enable 'Charge Stars for Messages' in the Permissions section.