Gmail and Google Workspace · permanent error
550 5.7.1: encoded word in a header where it is not allowed
Gmail rejected the message because a header contains RFC 2047 encoded-word text in a place where that encoding is not allowed.
- 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 Encoded-word syntax is not permitted in message header…
What it means
RFC 2047 encoded words, strings such as =?UTF-8?B?...?=, let headers carry non-ASCII text, but only in certain places: free text such as the Subject, and the display name in an address. They may not appear inside the address itself or in structured headers such as Message-ID. The bounce names the header where Gmail found one. The cause is sending software that encodes more of a header than it should.
Common causes
- Software that encodes the whole address, not only the display name.
- Encoded words in structured headers such as Message-ID or Date.
How to fix it
- 01Check the header named in the bounce in the raw message.
- 02Encode only display names and free text, and leave addresses in plain ASCII inside the angle brackets.
- 03Update the mail library, or fix the code that encodes headers.
- 04Resend once the header is fixed.
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
- 550 5.7.1Unicode character in a header.Gmail rejected the message because a header that must stay plain ASCII contains a Unicode character.
- 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