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Gmail and Google Workspace · permanent error

550 5.7.0: relay denied: sender not registered

Google's SMTP relay refused your mail because it comes from an IP or domain that is not registered in your Google Workspace account's relay settings.

Gmail
Provider
Permanent (5xx)
Class
Sources checked
By , email deliverability consultant
Author

At a glance

Code
550 5.7.0
Temporary or permanent
PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
Who has to act
The sender. The fix is on the sending side: your domain, your server or your list.
What the server says
550 5.7.0 Email relay denied… Invalid credentials for relay for one of the domains in:

What it means

This is a Workspace SMTP relay error. Mail sent to smtp-relay.gmail.com is accepted only when Google can tie it to your Workspace account: the sending IP is listed in the SMTP relay service setting, or the client signs in with SMTP AUTH, and the domain it presents in HELO or MAIL FROM is one of yours. Here the IP or the domain did not match, so relay was denied. Google's relay page adds that the HELO name should ideally be the sending device's fully qualified domain name, and that MAIL FROM must give the sender address properly.

Common causes

  • The sending device's public IP is not in the SMTP relay service setting.
  • The device's public IP changed, for example after an ISP or network change.
  • The HELO name or MAIL FROM domain is not a domain in your Workspace account.

How to fix it

  1. 01Find the public IP the device sends from; the bounce shows the one Google saw.
  2. 02In the Admin console, add that IP to the SMTP relay service setting, or switch the device to SMTP AUTH.
  3. 03Configure the device to send HELO with a fully qualified name in your domain, and a MAIL FROM address on a domain you own.
  4. 04Send a test, and check Email Log Search if it still fails.

Sources

What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.

  1. 550 5.7.1Relay IP does not match the sending domain.Google's SMTP relay knows your IP, but the mail's sending domain is not one that IP is registered to relay for in your Workspace account.GmailPermanent
  2. 550 5.7.0Email sending denied.Google refused to send this mail through its servers for your account, and its reply refers you to the SMTP relay error documentation.GmailPermanent
  3. 550Mailbox unavailable.The receiving server permanently refused the message for this recipient: the mailbox does not exist, cannot be reached, or the server rejected the message by policy.StandardPermanent
  4. 5.7.0Security or policy refusal, unspecified.The message or session was refused for a security or policy reason that the server did not describe more precisely, or chose not to reveal.StandardPermanent

5.7.0 at other providers

  1. 550 5.7.0Message classified as spam or virus.The Telekom spam filter classified your message as spam or as carrying a virus and rejected it after the DATA phase. False positives can be reported.TelekomPermanent

All 108 Gmail codesEvery code in the wikiPaste your own bounce

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