Today, we are announcing that, beginning in January 2025, Exchange Online will begin enforcing an external recipient rate limit of 2,000 recipients in 24 hours.
Exchange Online does not support bulk or high-volume transactional email. We have not enforced limiting of bulk email until now, but we plan on doing so with the introduction of an External Recipient Rate (ERR) limit. The ERR limit is per user/mailbox and being introduced to help reduce unfair usage and abuse of Exchange Online resources.
What about the Recipient Rate Limit?
Exchange Online enforces a Recipient Rate limit of 10,000 recipients. The 2,000 ERR limit will become a sub-limit within this 10,000 Recipient Rate limit. There is no change to the Recipient Rate limit, and both of these will be rolling limits for 24-hour windows. You can send to up to 2,000 external recipients in a 24-hour period, and if you max out the external recipient rate limit then you will still be able to send to up to 8,000 internal recipients in that same period. If you don't send to any external recipients in a 24-hour period, you can send to up to 10,000 internal recipients.
How will this change happen?
The new ERR limit will be introduced in 2 phases:
What are the options for customers who have business needs that exceed the ERR limit?
If you have a cloud-hosted mailbox that needs to exceed the ERR limit, you can move to Azure Communication Services for Email, which is designed specifically for high volume email sent to recipients external to your tenant.
Exchange Online Transport Team
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