Generic SMTP
554 5.7.1 Delivery not authorized — read the policy reason
554 5.7.1
RFC 3463 defines 5.7.1 broadly: the sender is not authorized to send to the destination or the receiver refuses the message under a security policy. It is not one universal blocklist or authentication error. The sentence and provider identifier beside the code determine whether the real issue is relay permission, SPF/DKIM/DMARC, reputation, content, recipient policy, or another local rule.
How to fix it
- 1
Keep the full diagnostic sentence
Find the text immediately after 5.7.1 and any official provider URL or proprietary code. That detail selects the correct remediation.
- 2
Check authentication when it is named
Verify that the actual sending path passes SPF or DKIM and that DMARC aligns with the visible From domain. A DNS record alone does not prove the message passed.
- 3
Check relay and recipient permissions
If the reply says relay denied, access denied, or not permitted, confirm the sender authenticated to the correct submission server and that connectors or recipient restrictions allow the route.
- 4
Use the receiver's remediation path
For reputation, block, or content policy responses, fix the named cause and follow the receiving provider's postmaster process. Do not rotate infrastructure to evade enforcement.
Meaning current as of 2026-07-15, cross-checked against the provider's own documentation. Providers do occasionally redefine codes — if this doesn't match what you're seeing, the source link is the authoritative reference.