Gmail 552 5.3.4: message exceeds size limits
552 5.3.4Message exceeds Google’s size limitPermanent: retrying will not helpFrom Gmail and Google Workspace
552-5.3.4 Your message exceeded Google’s message size limits. Please visit https://support.google.com/mail/?p=MaxSizeError to view our size guidelines. - gsmtp
What it means
Gmail accepts incoming messages up to 50 MB in total, measured after MIME encoding. Anything larger is refused with 5.3.4, which RFC 3463 names “message too big for system”. The limit applies to the whole message: body, every attachment, and headers together.
Base64 encoding adds about a third to file sizes, so a 40 MB attachment becomes roughly 53 MB on the wire. That is why senders are surprised: the file looked small enough. When a Gmail user sends, the composer limit is 25 MB and larger files are converted to Drive links.
Likely causes
- A single attachment above roughly 37 MB before encoding.
- Several moderate attachments that add up past the limit.
- Embedded high resolution images in an HTML signature or newsletter repeated across a long reply chain.
- A scanner or application that attaches uncompressed files.
How to fix it
- Check the size of the sent item in your mail client or the size reported in your MTA logs.
- Compress files into a zip archive or reduce image resolution, keeping the encoded total under 50 MB.
- For large files, upload to a file share and send a link.
- Split very large sets of files across several messages.
Checks that apply
- SMTP Diagnostics Shows the SIZE value a mail server advertises in its EHLO reply, which tells you the limit in bytes.
- MX Lookup Confirms the recipient domain is on Google, so the Google limit applies rather than another provider’s.
FAQ
- Is the Gmail limit 25 MB or 50 MB?
- Gmail can receive messages up to 50 MB. 25 MB is the limit for attachments a Gmail user sends.
- Can a Workspace admin raise it?
- Admins can lower the limit for their domain but cannot raise it above Google’s maximum.