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SMTP error code · Gmail / Google Workspace

550 5.7.40: Gmail blocked mail from a domain without a DMARC policy

550 5.7.40 Permanent failure (5xx): the message bounced
By iBlockSpam Team Checked against sources 3 sources How we check our content
What it means

Gmail blocked (550) or rate limited (421 4.7.40) your message because the sending domain has no DMARC record, or its record doesn't specify a policy. Gmail requires DMARC from bulk senders.

What the bounce says
550 5.7.40 Your message was blocked because the sending domain doesn't have a DMARC record or the DMARC record doesn't specify a DMARC policy.

Start of the 5.7.40 message in Google's Gmail SMTP errors and codes reference; it continues "Gmail requires all bulk email senders to add a DMARC record to their sending domain."

What 550 5.7.40 means

Google lists two versions. 421 4.7.40 says your email has been rate limited because the sending domain doesn't have a DMARC record, or the record doesn't specify a policy. 550 5.7.40 says the message was blocked for that reason. Both say Gmail requires all bulk email senders to add a DMARC record to their sending domain.

A DMARC record is a TXT record at _dmarc.yourdomain with at least a version and a policy, for example v=DMARC1; p=none. Google's sender guidelines say that for senders of more than 5,000 messages a day to Gmail accounts, the DMARC enforcement policy can be set to none. So publishing a valid record is enough to clear this error; moving to quarantine or reject is a separate, later step.

Don't confuse this with another Gmail error that shares the code: 504 5.7.40 "Unrecognized authentication type" (and "XOAUTH is no longer supported") is about SMTP sign-in to Google, not DMARC. If your bounce mentions DMARC, it's the DMARC requirement; if it came from your own client signing in, it's an authentication setting.

Likely causes

  • The sending domain has no TXT record at _dmarc.
  • The DMARC record has no p= policy tag or a syntax error, so it isn't valid.
  • Mail is sent from a subdomain whose organizational domain has no DMARC record.

How to fix it

If you sent the message

  1. Publish a DMARC record such as v=DMARC1; p=none; rua=mailto:<your report address>.
  2. Check the record has exactly one v=DMARC1 tag first and a p= tag.
  3. Make sure SPF and DKIM pass and align for every service before you tighten the policy.
  4. Read the aggregate reports, then move toward quarantine or reject when legitimate mail passes.

If you're the recipient or their admin

  1. No action needed at Gmail: the sender has to publish DMARC.
DMARC Record Generator DMARC Checker DMARC Report Analyzer

Frequently asked questions

Does Gmail's 5.7.40 require a DMARC policy of reject?

No. Google's sender guidelines say the DMARC enforcement policy for bulk senders can be set to none. The error means there's no valid record or no policy in it, so publishing v=DMARC1; p=none clears it.

Why do I see 504 5.7.40 when signing in to Gmail SMTP?

That's a different Gmail error with the same enhanced code: "Unrecognized authentication type" or "XOAUTH is no longer supported". It concerns how your app signs in to Google's SMTP server, not DMARC.

Sources

  1. Gmail SMTP errors and codes (Google Workspace Admin Help)
  2. Email sender guidelines (Gmail Help)
  3. RFC 9989: Domain-based Message Authentication, Reporting, and Conformance (DMARC)

Provider messages are quoted as the provider publishes them. Servers can change their wording, so the bounce you received may differ slightly.

Related codes

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