550 5.7.236: onmicrosoft.com domain reached its external limit
The tenant sent to more than 100 external recipients in 24 hours from its onmicrosoft.com domain, which Microsoft intends for testing only.
- Microsoft
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 550 5.7.236
- Temporary or permanent
- PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
550 5.7.236 …exceeded its daily limit for sending email to external recipients from your tenant's onmicrosoft.com domains
What it means
Every Microsoft 365 tenant gets an onmicrosoft.com domain, its MOERA domain. Microsoft intends it for testing and limits outbound mail from it to 100 external recipients per tenant in a rolling 24 hours, counted after list expansion. When the limit is hit, further mail to outside recipients from those domains bounces with 550 5.7.236 while the tenant is throttled. Inbound mail is not affected. The lasting fix is to add a custom domain to the tenant and send all external mail from it.
Common causes
- Users or applications send external mail from the tenant's onmicrosoft.com address instead of a custom domain.
- A new tenant started sending before its custom domain was added.
How to fix it
- 01Add and verify a custom domain in Microsoft 365.
- 02Change user primary addresses and application senders to the custom domain.
- 03For mail already blocked, wait for the 24-hour window to move on.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- Email nondelivery reports and SMTP errors in Exchange Onlinelearn.microsoft.com
- Exchange Online limitslearn.microsoft.com
Related codes
- 5.7.233Tenant reached its external recipient limit.The Microsoft 365 tenant sent to more external recipients in 24 hours than its tenant external recipient rate limit allows.
- 5.7.232Trial tenant reached its external recipient limit.A Microsoft 365 trial tenant sent to more external recipients in 24 hours than its tenant external recipient rate limit allows.
Further reading
All 111 Microsoft codesEvery code in the wikiPaste your own bounce