552 5.3.4 Message size exceeds fixed maximum message size
The message is larger than the receiving server allows. Limits are set per server and are often lower than people expect: 25 MB at Gmail, 150 MB at Exchange Online but commonly 35 MB per tenant, 10 MB on many shared hosts. Attachments grow by about a third when encoded for email, so a 20 MB file becomes a 27 MB message.
What the server replies
552 5.3.4 Error: message file too big
- Sent by
- Any mail server
- Type
- PermanentRetry fails
- About
- Message size
- Enhanced code
- 5.3.4
Who sends it
Any server with a size limit, usually after DATA or at MAIL FROM when the client announces the size with the SIZE extension. Postfix returns "message file too big" against message_size_limit; Exchange says "RESOLVER.RST.RecipSizeLimit" or "Message size exceeds fixed maximum"; Gmail says "552-5.2.3 Your message exceeded Google's message size limits".
Why it happens
- A large attachment, especially video or an unoptimised PDF.
- An email thread that has accumulated every previous attachment through repeated forwarding.
- An HTML message with images embedded as base64.
- A per-recipient limit lower than the server's general limit.
How to fix it
Share a link instead
Upload the file to a drive and send the link. This is the right answer for anything above a few megabytes.
Compress or split
Zip documents, export PDFs at a lower resolution, or send attachments across two messages.
Read the SIZE in EHLO
An SMTP test shows the server's advertised maximum in the EHLO reply, so you know the limit before sending.
Check it yourself
These free tools show the records and connections behind this code for your own domain or server.
Related codes
- 452 4.2.2 Mailbox full / over quotaThe recipient's mailbox has no room for the message.
- 552 5.2.2 The email account that you tried to reach is over quotaThe recipient's Google storage is full, so Gmail cannot accept new mail for them.
- 452 4.5.3 Too many recipientsYou tried to address one message to more recipients than the server accepts in a single transaction.
Sources
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