It is intended behavior that users will get all messages of his group. Most of the messaging system done by this rule. Eg. if you open a facebook group message and later add any user, he will receive all messages previously sent also.
It is intended behavior that users will get all messages of his group. Most of the messaging system done by this rule. Eg. if you open a facebook group message and later add any user, he will receive all messages previously sent also.