New External Recipient Rate Limit for Exchange Online

New External Recipient Rate Limit for Exchange Online

Today, I have an important announcement to make. Starting in January 2025, Microsoft will implement a new external recipient rate limit for Exchange Online. From that date, you will be able to send emails to a maximum of 2,000 external recipients within a 24-hour period.

Why This Change?

Microsoft has stated that Exchange Online does not support bulk or high-volume transactional email. Until now, there has been no enforced limit on bulk email sending. However, to ensure fair use of resources and prevent abuse, Microsoft is introducing a new External Recipient Rate (ERR) limit. This change is aimed at enhancing service quality and making resource usage more efficient.

When Will This Happen?

The new ERR limit will be implemented in two phases:

  • Phase 1: Starting January 1, 2025, the limit will apply to cloud-hosted mailboxes of all newly created tenants.
  • Phase 2: Between July and December 2025, the limit will be applied to cloud-hosted mailboxes of existing tenants.

How This Will Affect Your Organization

Currently, Exchange Online enforces a Recipient Rate limit of 10,000 recipients for cloud-hosted mailboxes. The new 2,000 recipient ERR limit will be a sublimit within this 10,000 recipient cap. Both the Recipient Rate limit and the ERR limit will operate as rolling limits within a 24-hour window.

  • External Recipients: You can send to up to 2,000 external recipients within a 24-hour period.
  • Internal Recipients: If you reach the 2,000 external recipient limit, you can still send to up to 8,000 internal recipients in the same 24-hour period.
  • Combined Limits: If no external recipients are contacted within a 24-hour period, you can send to up to 10,000 internal recipients.

Preparing for the Change

To align with these new limits, I recommend starting to plan now. Review your email sending practices and ensure they fit within the new ERR limit. This change may particularly impact those who rely on sending bulk emails to external recipients. Consider strategies to segment your email lists or stagger email sends over multiple days if necessary.

If your organization sends bulk emails or plans to send to over 2,000 external recipients, I recommend using third-party providers for the mailboxes used for this purpose. These providers can offer more suitable solutions for high-volume email sending.


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