Smart Notifications allow the user to avoid their phone ringing for every single message they receive in a group.

With this system, the phone will notify the user only for a few number of messages sent in a set time.

The default value is 2 messages in 1 minute ( this value works for WP and iOS, where it can't be changed).

On Android, you can change both values (number of messages, time) directly from the "Notifications and Sounds" setting of a group.