550 5.7.350
550 5.7.350 Tenant Policy Block
The recipient tenant rejected the message due to custom policies or allow/block lists.
Tenants can configure stricter requirements than Microsoft’s defaults. If your domain fails their custom rules, you will see 5.7.350.
Severity
ERROR
Provider
Microsoft 365 / Outlook
Reference
Mitigation Portal
Last Reviewed
2025-06-01
How to Fix 550 5.7.350
Follow these steps to resolve this Microsoft 365 / Outlook SMTP error and restore normal delivery.
- ✓Ask the recipient administrator to add your domain or IP to their allow list.
- ✓Share authentication and encryption details to prove trustworthiness.
- ✓Split transactional and marketing streams to meet different policy expectations.
- ✓If multiple tenants reject you, evaluate your baseline list hygiene and cadence.
Helpful Resources
More Microsoft 365 / Outlook SMTP Codes
Keep these related troubleshooting guides handy while addressing 550 5.7.350.
Still experiencing Microsoft 365 / Outlook delivery issues?
Run your domain through our free deliverability tools or book a session with Bento's deliverability specialists.