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Error: "552 5.3.4 Message size exceeds fixed maximum message size"


Article ID: 171696


Updated On:


Messaging Gateway


  • The recipient mail server sends back a message of "552 5.3.4 message size exceeds fixed maximum message size".
  • This can occur from new inbound messages, outbound messages, or quarantine delivery.
  • Error can show in the Message Audit Logs or in brightmaillog.log (especially for quarantine delivery issues).

Example from the Message Audit Logs:


  • Messaging Gateway


Root cause is usually due to the accepting mail server configuration. 
To verify these settings with the SMG and the mail server.
  1. From the SMG CLI interface (as admin), run telnet <mailserverhost> 25 and view 250-SIZE value.
  2. If the mail server SIZE is smaller than the size of the email delivery, then the mail server will reject the delivery.


Ensure the size allowed for the mail server is the same or larger than the size of the mail that is delivered.

If Exchange configuration is necessary, please see the following Microsoft TechNet links for more information:

If another mail server is being used, please refer to your mail server's documentation or support.