5.7.236: onmicrosoft.com domain hit 100 external recipients
Exchange Online returns 5.7.236 when your tenant sent to more than 100 external recipients in 24 hours from its onmicrosoft.com domain. Microsoft says those domains are for testing only. Add your own domain to the tenant and send from it; inbound mail is not affected.
The exact message
Microsoft 365 / Exchange Online
5.7.236 Your message can't be sent because your tenant has exceeded its daily limit for sending email to external recipients from your tenant's onmicrosoft.com domains
Why it happens
- Mailboxes are sending with an @<tenant>.onmicrosoft.com address.
How to fix it
- Add and verify a custom domain in the tenant.
- Change users’ primary address to the custom domain so outbound mail uses it.
If you send cold email
Never send outreach from an onmicrosoft.com address; it is capped at 100 external recipients a day across the tenant and looks untrustworthy to recipients.
How WarmHawk handles it
WarmHawk never sends more than a mailbox’s own daily cap, spaces sends from one mailbox at least 8 minutes apart with random jitter, and starts a newly warmed mailbox at 5 campaign emails a day, growing 20% a day. A temporary failure is retried with backoff (30 minutes, then doubling) and the lead is suppressed after 4 attempts, so a throttled mailbox is never hammered. How WarmHawk works →
Check your domain now
These free checkers read your live DNS: no account, up to 15 domains at once.
Related bounce codes
- 5.7.233Tenant exceeded its daily external recipient limit
- 5.7.750Blocked from sending from unregistered domains
Sources, checked 2026-09-29: Microsoft Learn: NDRs and SMTP errors in Exchange Online. Have a different bounce? Paste it into the decoder →
Questions
5.7.236 questions
What does 5.7.236 mean?+
Exchange Online returns 5.7.236 when your tenant sent to more than 100 external recipients in 24 hours from its onmicrosoft.com domain. Microsoft says those domains are for testing only. Add your own domain to the tenant and send from it; inbound mail is not affected.
Is 5.7.236 a temporary or permanent error?+
Permanent. The message will not be retried, and sending it again unchanged will fail the same way until the cause is fixed.
How do I fix 5.7.236?+
Add and verify a custom domain in the tenant. Change users’ primary address to the custom domain so outbound mail uses it.