550 5.7.1: relay 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.
- Gmail
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 550 5.7.1
- Provider
- Gmail and Google Workspace
- 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 5.7.1 …The IP address you've registered in your Workspace SMTP Relay service doesn't match the domain…
What it means
Your IP is registered in a Workspace account's SMTP relay service setting, but the account the message is sent from belongs to a domain that does not match, or the envelope sender is empty, so Google cannot tell which of your domains the mail belongs to. The reply spells out the fix. To relay mail from a domain that is not registered in your Workspace account, or with an empty envelope-from such as a bounce, the mail server must either use SMTP AUTH to identify the sending domain or present one of your domain names in HELO or EHLO.
Common causes
- A shared mail server relaying mail for a domain that is not in your Workspace account.
- Bounces or other messages with an empty envelope sender passed to the relay.
- A HELO name that is not one of your Workspace domains.
How to fix it
- 01Configure the mail server to sign in with SMTP AUTH as a Workspace user when it relays.
- 02Or set its HELO or EHLO name to a host in one of your registered domains.
- 03Add any other domains that send through the relay to your Workspace account, or send their mail another way.
- 04Test with a message from each domain and with an empty-sender message.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- Gmail SMTP errors and codes (Google Workspace Admin Help)knowledge.workspace.google.com
- SMTP relay service error messages (Google Workspace Admin Help)knowledge.workspace.google.com
Related codes
- 550 5.7.0Relay 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.
- 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.
- 5.7.1Delivery not authorised.The receiving server refuses the message because this sender is not allowed to send to this recipient, as a result of filtering by host or by recipient.
5.7.1 at other providers
- 550 5.7.1Not authorized to send to this recipient.You do not have permission to send to this recipient, typically a group restricted to certain senders or a recipient protected by a mail flow rule.
- 550 5.7.1Public folder does not accept external mail.An external sender wrote to a mail-enabled public folder in Microsoft 365, which by default accepts mail only from authenticated senders.
- 550 5.7.1Sending IP blocked by Proofpoint Dynamic Reputation.Proofpoint’s IP reputation system has your sending IP on its block list because it has seen spam or viruses from it, so Proofpoint customers refuse your mail.
- 550 5.7.1SPF check failed.The recipient’s Cisco Secure Email gateway checked SPF, found your server not authorised for the sender domain, and its policy rejects that result.
- 550 5.7.1Rejected under your domain’s DMARC policy.Your message failed DMARC, your domain’s DMARC record asks receivers to reject such mail, and the recipient’s Cisco gateway did so.
- 550 5.7.1DMARC verification failed permanently.The Cisco gateway hit a permanent failure while verifying DMARC for your message, and the recipient’s policy rejects such mail. Cisco does not say what produces that failure.
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