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

URL: https://iblockspam.com/smtp-errors/550-5-7-40
Last updated: 2026-10-22

Code: 550 5.7.40 (permanent failure, the message bounced)
Provider: Gmail / Google Workspace

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."

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.

## Common 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 (sender)

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

## How to fix it (recipient or admin)

- No action needed at Gmail: the sender has to publish DMARC.

**Q: 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.

**Q: 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:
- Gmail SMTP errors and codes (Google Workspace Admin Help): https://knowledge.workspace.google.com/admin/support/troubleshooting/gmail-smtp-errors-and-codes
- Email sender guidelines (Gmail Help): https://support.google.com/mail/answer/81126
- RFC 9989: Domain-based Message Authentication, Reporting, and Conformance (DMARC): https://www.rfc-editor.org/rfc/rfc9989

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