Should I retry a 550 5.7.1 error?

No. 550 is a permanent failure, so the message will never be delivered no matter how many times you try. Remove the address — repeated sends to permanent failures are one of the main signals mailbox providers use to throttle a sender.

How do I fix SMTP 550 5.7.1?

Check your SPF, DKIM and DMARC records first — a policy rejection usually means an alignment failure. Run a full audit on your sending domain.

Permanent failure — do not retry

SMTP 550 5.7.1

message refused by policy

SMTP 550 5.7.1 means the recipient's server recognised the address but refused the message on policy grounds — failed authentication, a blocklisted sending IP, or content its filters rejected. Unlike 5.1.1, the mailbox is fine; the problem is you, or your sending infrastructure.

How it appears

550 5.7.1 Unauthenticated email from example.com is not accepted due to domain's DMARC policy.

550 5.7.1 Service unavailable; Client host [203.0.113.5] blocked using Spamhaus

550 5.7.1 Message rejected due to content restrictions

What causes it

SPF, DKIM or DMARC failed, and the recipient domain publishes p=reject.
Your sending IP or domain appears on a blocklist the recipient consults.
The recipient server requires authentication you did not provide, or refuses relaying.
Content filtering rejected the message outright rather than filing it as spam.

How to fix it

In order — try the first one first.

Check your SPF, DKIM and DMARC records first — a policy rejection usually means an alignment failure. Run a full audit on your sending domain.
Check whether your sending IP is on a major blocklist. A listing explains a sudden, total delivery failure that otherwise looks inexplicable.
Read the text after the code. Most servers name the specific reason, and many include a URL explaining their policy.
If it started suddenly with no infrastructure change, look for a bounce or complaint spike that triggered the listing.

Common questions

What does SMTP 550 5.7.1 mean?: SMTP 550 5.7.1 means the recipient's server recognised the address but refused the message on policy grounds — failed authentication, a blocklisted sending IP, or content its filters rejected. Unlike 5.1.1, the mailbox is fine; the problem is you, or your sending infrastructure.
Should I retry a 550 5.7.1 error?: No. 550 is a permanent failure, so the message will never be delivered no matter how many times you try. Remove the address — repeated sends to permanent failures are one of the main signals mailbox providers use to throttle a sender.
How do I fix SMTP 550 5.7.1?: Check your SPF, DKIM and DMARC records first — a policy rejection usually means an alignment failure. Run a full audit on your sending domain.

Last reviewed 2026-09-11