Incoming email messages are receiving a delivery failure notification of "552 5.3.4 message size exceeds fixed maximum message size". The maximum message size of email is lower than what has been configured in the Symantec Brightmail Gateway. For example an email with an 8 MB attachment is getting rejected although the message size limits in the Brightmail has been increased from the default 10 MB to 15 MB and the message size limit in the downstream mail server is set to 10 MB.
552 5.3.4 message size exceeds fixed maximum message size.
The Symantec Brightmail Gateway will fail to deliver the message if the downstream mail server only accepts email messages with a total size of 10 MB. An overhead of 30-35% should be added for each email message when estimating the total size of the message. For example, an email containing an 8 MB attachment could cause the actual message size to be 11 MB. This could exceed the message size allowed by the downstream mail server.
The Symantec Brightmail Gateway is performing as designed and the issue lies with the downstream mail server's allowed message size limit.
It is suggested to increase the message size limit on the downstream mail server while considering the overhead percentage of messages. To know which downstream MTA is rejecting the message, check the details of a message in the Message Audit Logs. The message "Delivery Failure - Attempted Delivery to: 192.168.1.20" indicates the IP of the rejecting downstream mail server, in this case 192.168.1.120.
Symantec Brightmail Gateway 8.x or 9.x
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