When you send a message through Symantec Messaging Gateway (SMG), the message is rejected during the SMTP conversation with the response, "552 5.3.4 message size limit exceeded."
This SMTP response may come to your attention in one of several ways:
In the log file maillog:
ML-REJECT: Rejection on: 192.168.1.195:25,200, sent to host: 192.168.100.101:53390, Audit ID c6d429c3-b7cdcae000000c5f-b0-4b4f16ea800e, 552 5.3.4 message size limit exceeded
Increase the maximum message size for both Inbound and Outbound SMTP to allow the message.