Whatsapp is an immensely popular chatting app used by 1.5 Billion people worldwide. It has an easy interface and can be used powerfully with Odoo. Pragmatic has developed an Odoo app which allows users to use the Whatsapp Application to send messages via Odoo from mass messaging. In whatsapp 256 contacts can be added in one group so if you create an odoo group with multiple contacts, multiple partners will be added in the one odoo group.