550 5.4.1
550 5.4.1 Recipient Address Rejected
The recipient mailbox is invalid or blocked at the tenant level.
If the address is wrong or an admin has blocked inbound mail, Microsoft returns 5.4.1. Treat invalid addresses as hard bounces.
Severity
ERROR
Provider
Microsoft 365 / Outlook
Reference
Mitigation Portal
Last Reviewed
2025-06-01
How to Fix 550 5.4.1
Follow these steps to resolve this Microsoft 365 / Outlook SMTP error and restore normal delivery.
- ✓Verify address spelling and remove invalid recipients from future sends.
- ✓Ask the recipient to confirm their mailbox or alias configuration.
- ✓Request a tenant-level allow entry if the recipient intentionally blocks external mail.
- ✓Update CRM or marketing databases to prevent repeat attempts.
Helpful Resources
More Microsoft 365 / Outlook SMTP Codes
Keep these related troubleshooting guides handy while addressing 550 5.4.1.
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