Monthly Active Users (MAU)
MAU stands for Monthly Active Users. Any unique phone number that interacts with your official WhatsApp number. An MAU is counted only if there is at least one incoming message and one outgoing message to that number.
Fair Use Policy
The Monthly Active Users fee per month is subject to a fair use policy of maximum 50 messages (of any type) per customer per month.
You will be charged one additional Monthly Active User fee for every 50 messages exchanged with one user. For example, if you exchange say, 101 messages with a single user then you will be charged for three users.