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 signifi...
Published Jan 06, 2026
Version 1.0
Blog Post
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.