# 550 5.7.1 Bounce: Delivery Not Authorized, Message Refused

URL: https://email-validation.org/bounce-codes/550-5-7-1/
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 5.7.1:** “Delivery not authorized, message refused” in the IANA registry (RFC 3463), in the group security or policy status (RFC 3463 §3.8).

A 550 5.7.1 reply means the receiving server refused your message because of a policy. The code is used for many different policies, so the words after it are what tell you which one, and what to fix.

## What it means

[RFC 3463 §3.8](https://www.rfc-editor.org/rfc/rfc3463) defines X.7.1 as "delivery not authorized, message refused": the sender is not allowed to deliver to this host or this recipient, because of filtering. The 550 basic code is a permanent refusal ([RFC 5321 §4.2.1](https://www.rfc-editor.org/rfc/rfc5321)). Some servers send the same enhanced code as `554 5.7.1`. The meaning is the same: a policy said no, and retrying unchanged will not help.

## Telling the causes apart

Look for these clues in the text after the code:

- **"Relay" or "unable to relay":** you sent through a server that does not accept mail for that domain from you, usually because the app did not sign in. Microsoft uses 5.7.1 for this, and for a client that was not authenticated.
- **"Not authorized" or "not allowed to send to":** the recipient (or its group) blocks you. Microsoft 365 has its own codes for groups: [5.7.124](https://email-validation.org/bounce-codes/5-7-124/) and [5.7.133](https://email-validation.org/bounce-codes/5-7-133/).
- **"Unsolicited", "reputation" or "spam":** a content or reputation filter. Gmail uses 550 5.7.1 for likely unsolicited mail and for very low IP or domain reputation.
- **Header words ("From", "Message-ID", "header"):** a malformed message. Gmail rejects a missing or invalid From header, multiple From addresses, a missing Message-ID, and duplicate or badly encoded headers.
- **"Not allowed to send directly":** your IP should hand mail to its provider's relay instead.
- **"IPv6":** IPv6 sending without a PTR record or authentication.
- **A blocklist name or IP ban:** see [5.7.606](https://email-validation.org/bounce-codes/5-7-606/) for Microsoft.

## How providers use it

Gmail lists all of the above, plus a domain policy that prohibits the mail, relay credentials that do not match the sending domain, and a daily relay limit ([Google's SMTP error reference](https://support.google.com/a/answer/3726730)). Microsoft's meanings are in its [NDR reference](https://learn.microsoft.com/en-us/troubleshoot/exchange/email-delivery/ndr/non-delivery-reports-in-exchange-online). Yahoo documents permanent policy refusals with plain 553 or 554 codes, for DMARC or DKIM failures, prohibited content or a blocklist listing ([Yahoo's error codes](https://senders.yahooinc.com/smtp-error-codes/)).

## How to fix it

1. Relay: turn on SMTP authentication in the sending app, or send through the server that handles your own domain.
2. Recipient restriction: ask the recipient to have their admin allow you.
3. Reputation: fix authentication ([SPF](https://email-validation.org/tools/spf-checker/), [DKIM](https://email-validation.org/tools/dkim-checker/), [DMARC](https://email-validation.org/tools/dmarc-checker/)) and follow [Google's sender guidelines](https://support.google.com/a/answer/81126).
4. Headers: send exactly one valid From address and a Message-ID.

## What to do with the address

Usually keep it: most 5.7.1 refusals are about the sender or the message. Remove it only when the text says the recipient itself was rejected.

## Related codes

- [421 4.7.0](https://email-validation.org/bounce-codes/421-4-7-0/): Temporarily refused: reputation, DNS or TLS
- [550 5.7.26](https://email-validation.org/bounce-codes/550-5-7-26/): Unauthenticated: SPF and DKIM failed, or DMARC rejected it
- [5.7.606](https://email-validation.org/bounce-codes/5-7-606/): Banned sending IP (Microsoft)
- [5.7.133](https://email-validation.org/bounce-codes/5-7-133/): The group or mailbox takes no mail from outside (Microsoft 365)

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.