# 550 5.7.40 Bounce: No DMARC Policy (Gmail)

URL: https://email-validation.org/bounce-codes/550-5-7-40/
Updated: 2026-11-06

> Documentation index: https://email-validation.org/llms.txt

**At a glance**

- **Type:** permanent failure (class 5, RFC 3463 §2). The sending server does not retry; sending the same message again fails the same way until the cause is fixed.
- **Basic code 550:** “Requested action not taken: mailbox unavailable (e.g., mailbox not found, no access, or command rejected for policy reasons)” (RFC 5321 §4.2.3).
- **Enhanced code 5.7.40:** not in the IANA registry; the group is security or policy status (RFC 3463 §3.8).
- **Who uses it:** Google (Gmail): the sending domain has no DMARC policy.

A 5.7.40 bounce from Gmail means your sending domain has no DMARC record, and Gmail requires one from bulk senders. Publishing a basic DMARC policy is enough to clear this particular error.

## What it means

This is Google's code, and its meaning comes from Google. [Google's SMTP error reference](https://support.google.com/a/answer/3726730) lists it in two forms:

- **421 4.7.40:** the domain has no DMARC policy, and Gmail rate limits your mail. Your server will retry, but deferrals continue until the record exists.
- **550 5.7.40:** the same reason, and the message is refused.

DMARC is a DNS record on your From: domain. It tells receivers what to do with mail that fails SPF and DKIM alignment, and where to send reports.

## What Gmail requires

[Google's sender guidelines](https://support.google.com/a/answer/81126) split senders in two:

- **All senders:** SPF or DKIM, valid forward and reverse DNS, and TLS.
- **Bulk senders** (around 5,000 or more messages a day to personal Gmail accounts): SPF, DKIM and DMARC. The DMARC policy may be `p=none`. The From: domain must align with SPF or DKIM, and marketing and subscribed messages need one-click unsubscribe.

So the policy does not have to block anything. It only has to exist.

## Common causes

- The domain never had a DMARC record.
- The record sits at the wrong host name, or has a syntax error, so receivers do not find a valid policy.
- You started sending from a new domain (a second brand, say) that was never given a record.
- A DNS change removed the record.

Google also lists `504 5.7.40` for an unrecognized authentication type when a client signs in: that is an SMTP AUTH problem, covered under [530 5.7.0](https://email-validation.org/bounce-codes/530-5-7-0/) and [535 5.7.8](https://email-validation.org/bounce-codes/535-5-7-8/), not DMARC.

## How to fix it

1. Look up your From: domain with the [DMARC checker](https://email-validation.org/tools/dmarc-checker/).
2. If there is no valid record, build one with the [DMARC generator](https://email-validation.org/tools/dmarc-generator/). Start with `p=none` and an address to receive aggregate reports.
3. Publish it in your DNS, then run the checker again.
4. Make sure SPF or DKIM passes for your From: domain, or DMARC will fail even with a record: see [5.7.32](https://email-validation.org/bounce-codes/5-7-32/) for alignment and the [SPF checker](https://email-validation.org/tools/spf-checker/) and [DKIM checker](https://email-validation.org/tools/dkim-checker/).
5. Read the reports for a few weeks. When every legitimate source passes, you can move to a stricter policy.
6. Resend, or let your queue retry the deferred mail.

## What to do with the address

Keep it. A 5.7.40 refusal is about your domain's DNS, never about the recipient's mailbox.

## Related codes

- [5.7.32](https://email-validation.org/bounce-codes/5-7-32/): From: domain not aligned with SPF or DKIM (Gmail)
- [550 5.7.26](https://email-validation.org/bounce-codes/550-5-7-26/): Unauthenticated: SPF and DKIM failed, or DMARC rejected it
- [550 5.7.27](https://email-validation.org/bounce-codes/550-5-7-27/): SPF failed for a bulk sender (Gmail), or the sender has a null MX

See [every bounce code](https://email-validation.org/bounce-codes/) in the dictionary.

Many bounces from addresses that do not exist can be avoided: check an address with our [free email checker](https://email-validation.org/email-checker/), or [clean a whole list](https://email-validation.org/bulk-email-verification/) before you send.