Message length exceeds administrative limit
Production Risk
Low — affects specific large messages, not overall sending reputation.
The message size exceeds the maximum message size limit set by the receiving mail administrator. The message has been permanently rejected.
- 1The message contains large attachments that exceed the server's per-message size limit.
- 2The sending client did not check the server's SIZE capability before sending.
- 3A base64-encoded attachment inflated the message size beyond the limit.
Attempting to deliver a message that exceeds the receiving server's configured maximum message size.
MAIL FROM:<sender@example.com> SIZE=52428800 # Server returns: 552 5.2.3 Message size exceeds fixed maximum message size
expected output
552 5.2.3 ...
Fix
Check SIZE capability and compress or link attachments
WHEN Before sending large messages
# Check server max size from EHLO response 250-SIZE 10485760 # If message exceeds limit, use a file sharing link instead: # Upload attachment to storage (S3, Drive, etc.) # Send a link in the email body instead of the attachment
Why this works
Checking the advertised SIZE limit in the EHLO response and substituting links for large attachments avoids the rejection.
✕ Retry sending the same oversized message
The size limit is administrative — the message will be rejected every time until its size is reduced.
RFC 3463 — Enhanced Mail System Status Codes
Content generated with AI assistance and reviewed for accuracy. Found an error? hello@errcodes.dev