Rate limits are in place to prevent malicious behavior and poor user experiences.
For more information, check out the Rate Limiting section of the Facebook Messenger support documentation.
Facebook Messenger Limits
The per-day rate limit is equal to 200 times the number of people the business can message via Messenger.
This metric is the number of people who have ever sent a message to the business on Messenger, not including people who have blocked or reported the business on Messenger.
There may be some constraints on your business’s ability to send messages to connections, such as limitations on how many messages you can send during certain time frames.
Messing Limits Example
One thousand (1000) Facebook Messenger users have engaged Brand X via Facebook Messenger. Ten (10) users have elected to block Brand X from future communications. How many messages can Brand X send?
Rate Limit = Number of Conversations * 200
Rate Limit = (1000 conversations – 10 blocked conversations) * 200
Rate Limit = 398,000
Brand X may send up to 398,000 messages per day.