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Exchange Online canceling the Mailbox External Recipient Rate Limit

The_Exchange_Team's avatar
The_Exchange_Team
Platinum Contributor
Jan 06, 2026

We’re announcing an important change: the Mailbox External Recipient Rate Limit in Exchange Online is being canceled indefinitely at this time.

Customers have shared that this limit creates significant operational challenges, especially given the limited capabilities of bulk sending offerings available today. Your feedback matters, and we’re committed to solutions that balance security and usability without causing unnecessary disruption.

Our goals remain the same:

  • Combat abuse of Exchange Online customers, like spam and malicious email activity.
  • Prevent misuse of Exchange Online, such as line-of-business (LOB) applications sending bulk email through Exchange Online.

However, we plan to address these issues in ways that are less disruptive to your business workflows. This means smarter, more adaptive approaches that protect the service while respecting your operational needs.

What’s not changing

The Recipient Rate Limit and the Tenant-level External Recipient Rate Limit mentioned in Exchange Online limits remain unchanged by this announcement.

Thank you for your continued feedback and partnership. We’re listening, and we’ll keep working to make Exchange Online secure, reliable, and customer friendly.

Exchange Online Transport Team

Published Jan 06, 2026
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5 Comments

  • Eriksrocha's avatar
    Eriksrocha
    MCT
    Jan 08, 2026

    This rate-limit update is important, but it does not address a major real-world abuse vector we’re seeing: spammers are using Azure Communication Services to send phishing emails using the azurecomm.net domain, and Microsoft is not taking action to stop it. This is resulting in real damage for customers and reputation issues for organizations that receive these messages. Please provide clear mitigation steps and enforce abuse controls for ACS mail traffic, because the current situation is unacceptable.

  • Frank Carius's avatar
    Frank Carius
    MVP
    Jan 07, 2026

    I'd call it "temporary" to allow mass mailings from authenticated EXO users. Admins should think about a proper solution instead of abusing EXO. Other Limits (TERRL, RRL, MailboxGrow, Client Throttling) are still in place.
    Even the limit of 2000 external recpients per mailbox can result in 2000 incoming answers/day, which is definitely not a great design for th usage. Admins should always separate "human mail" from "automated mail" with another domain, other MX-Record, other NDR-Handling etc and use Exchange Online for "people business. It is easy to use Azure Communication Services or 3rd party Services (Sendgrid, Mailgun, Mailchimp and many more) instead for mass mailing, newsletters, mailingliste, ERP/CRM-communication etc.

  • Tom_R_'s avatar
    Tom_R_
    Brass Contributor
    Jan 06, 2026

    Thank you! Also, are there any recommended solutions for receiving a large volume of mail as well as sending? I'm aware of using ACS for sending, but we need a solution for receiving a large volume of customer emails addressed to a single address.