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Microsoft Exchange Online will support a maximum of 2,000 recipients per 24 hours starting in 2025. This limit should significantly reduce the number of spam messages.

Until now, Exchange Online has not had a similar limitation. The upper limit consists of 10,000 recipients; this will remain unchanged. Only the number of external recipients (i.e., from outside the organization) will be curtailed. “There is no change to the Recipient Rate limit. If you send to less than 2,000 external recipients in a 24 hour period, you will still be able to send to 10,000 total recipients,” the Microsoft Exchange team said.


The so-called ERR (External Recipient Rate) limit will appear in phases. On Jan. 1, 2025, Microsoft will introduce the limit on new tenants in cloud-based mailboxes. Between July and December 2025, all existing users will follow.

The limit is per user, meaning an entire Exchange Online Tenant can send 2,000 messages times the number of users to external recipients. Organizations themselves have a limit that depends on the total number of users.

Spam reduction

Rate limiting is considered an essential means of reducing spam. In addition to these sending limits, Microsoft uses receiving limits. A user can receive a maximum of 3,600 messages per hour. This is especially important to Microsoft itself, however, because it prevents its own service from being overwhelmed.

Also read: Windows and Exchange Servers crash after March 2024 update