There’s no doubt Microsoft’s Exchange services have a lot to deal with these days, and the company itself warns that high message volumes for a mailbox or tenant means others would be impacted as well, with email delays hitting other customers by using unnecessary resources.

However, few people know that Microsoft actually had a soft limit in Exchange, only allowing a maximum of 3,600 messages per hour in an Exchange mailbox.

The company has never enforced this limitation, but starting with April 2021, this policy comes into effect in order to maintain the performance of Exchange services for everybody.

“These limits control the amount of messages that a user, group, or public folder can accept in a given hour. When a mailbox exceeds the threshold, any further messages to this mailbox will be throttled. The limit resets after an hour, allowing the mailbox to receive messages again. To ensure that all parties are aware, the throttled recipient will receive a notifi… (read more)