Permanent failure — do not retry
SMTP 552 5.3.4
message too big
SMTP 552 5.3.4 means the message is larger than the receiving server accepts. RFC 3463 defines X.3.4 as "message too big for system". Gmail returns it as "Your message exceeded Google's message size limits." The address is fine; the message needs to be smaller.
How it appears
552 5.3.4 Your message exceeded Google's message size limits.
552 5.3.4 Message size exceeds fixed limit
What causes it
- Large attachments. Encoding makes an attachment roughly a third larger in transit than on disk.
- Large embedded images in the HTML body.
- Headers that grew too large, usually from long forwarding chains.
How to fix it
In order — try the first one first.
- Replace attachments with a link to the file.
- Compress or resize images, and host them instead of embedding them.
- Do not remove the recipient. Resend a smaller message.
Common questions
- What does SMTP 552 5.3.4 mean?
- SMTP 552 5.3.4 means the message is larger than the receiving server accepts. RFC 3463 defines X.3.4 as "message too big for system". Gmail returns it as "Your message exceeded Google's message size limits." The address is fine; the message needs to be smaller.
- Should I retry a 552 5.3.4 error?
- No. 552 is a permanent failure, so the message will never be delivered no matter how many times you try. Remove the address — repeated sends to permanent failures are one of the main signals mailbox providers use to throttle a sender.
- How do I fix SMTP 552 5.3.4?
- Replace attachments with a link to the file.
Other 552 replies
Last reviewed 2026-09-11