Upcoming changes to mailbox receiving limits: Hot Recipients Throttling

To ensure optimal mail flow performance for all customers and protect the health of Exchange services, Microsoft is updating the way in which we enforce our mailbox receiving limits.

With the growth of digital transformation and remote work, having access to emails is more critical than ever. Microsoft is committed to delivering a safe and reliable email experience for all customers, which requires us to balance our service across mailboxes.

If a mailbox or tenant is allowing extremely high message volume, this can negatively impact other customers and cause email delays. Mailboxes that exceed our thresholds will consume resources from other mailboxes. As a large and global platform, we must enforce these limits to provide an equal experience for customers.

Starting in April 2021, we will progressively roll out the new enforcement, starting at a higher threshold and incrementally lowering it until we arrive at our established limit of 3600 messages per hour, per mailbox.

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