552 5.3.4: message headers too large
Gmail rejected the message because its header section as a whole is larger than Google allows, or holds too many header fields.
- Gmail
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 552 5.3.4
- 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
552 5.3.4 Your message exceeded Google's message header size limits.
What it means
Apart from the body, Gmail limits the header section of a message: its total size in bytes and the number of header fields. One version of the reply states both limits. Headers grow each time a message passes through a server, a gateway, a mailing list or a forwarding rule, so a message that has travelled through many systems, or software that writes long custom headers, can go over. Google links the reply to its page on Gmail message header limits. The message has to be changed before Gmail will accept it.
Common causes
- Many Received and authentication headers added by a long chain of forwarding or gateways.
- Software that writes large or numerous custom X- headers.
- Very long recipient lists in To or Cc.
How to fix it
- 01Inspect the headers with a header analyzer to see which fields are large or repeated.
- 02Remove unnecessary custom headers in the sending software.
- 03Shorten forwarding chains, or move long recipient lists to Bcc or a group address.
- 04Resend once the header section is smaller.
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
Related codes
- 552 5.3.4A single header is too large.Gmail rejected the message because one of its header fields holds a value longer than Google allows for a single header.
- 552 5.3.4Subject line too long.Gmail rejected the message because its Subject header is longer than Google's header size limits allow.
- 552Storage allocation exceeded.The receiving server aborted the message because it exceeded a storage limit, usually a full mailbox or a message larger than allowed.
- 5.3.4Message too big.The message is larger than the maximum size the receiving system accepts for any message, so it was refused and has to be made smaller.
5.3.4 at other providers
Further reading
All 108 Gmail codesEvery code in the wikiPaste your own bounce