MyChat Rights Group: "Forbid private dialogues with everybody, except private contact list"
A rule that limits range of users with whom you can open private dialogues.
If on, a user can open dialogues only with people from personal contacts. A person create such a list on their own.
You can also do it by using a script on the server (server scripts, the script №13: "Script to create a personal contact list by user groups automatically").
Notice, this rule is only limits outgoing attempts. If a bot or someone outside personal contacts sends a message, the server will allow this action by creating a new private dialogue where you can reply to this new person.
By default this rule is off.