Gmail and Google Workspace · permanent error
550 5.7.1: missing Message-ID header
Gmail rejected the message because it has no Message-ID header, or the one it has is not valid.
- 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 Messages missing a valid Message-ID: header are not accepted.
What it means
The Message-ID header gives each message a unique identifier. RFC 5322 says every message should have one, and Gmail enforces it: a message without a valid Message-ID is refused. Mail servers often add one when the client did not, so this tends to come from software that talks to Gmail directly and builds its own messages, or that writes a malformed value, for example without angle brackets or without an @ in the middle.
Common causes
- A script or application that sends messages without a Message-ID.
- A malformed Message-ID, such as one without angle brackets or an @.
How to fix it
- 01Check the raw headers of a sent message for a Message-ID line.
- 02Let your mail library or server generate it, in the form <unique@yourdomain>.
- 03Make sure each message gets a new value, since Gmail also limits repeated IDs.
- 04Resend once the header is present.
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
- Email sender guidelines (Gmail Help)support.google.com
Related codes
- 421 4.7.28Too many messages with the same Message-ID.Gmail is turning away further copies of a message because you have sent too many messages that carry the same Message-ID header.
- 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.
Further reading
All 108 Gmail codesEvery code in the wikiPaste your own bounce