SMTP Code: "552 5.3.4 message size limit exceeded" when sending messages


Article ID: 177785


Updated On:


Messaging Gateway


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:

  • The sending mail server generated a Non-Delivery Report to the original sender containing the response, "552 5.3.4 message size limit exceeded."
  • SMG may record a WARNING level entry on the MTA log containing the response, "552 5.3.4 message size limit exceeded."
  • When using a telnet client to send a test message to the SMG appliance you see the error, "552 5.3.4 message size limit exceeded."

In the log file maillog:

ML-REJECT: Rejection on:,200, sent to host:, 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.

To increase the maximum message size

  1. Log into the SMG Control Center.
  2. Click the Administration tab.
  3. In the left pane, click Hosts > Configuration.
  4. Click the underlined name of the host you want to configure.
  5. Click the SMTP tab.
  6. Scroll to the bottom of the page and click Advanced Settings.
  7. Under the Inbound settings, increase the number of bytes for "Maximum message size in bytes."
  8. Under the Outbound settings, increase the number of bytes for "Maximum message size in bytes."
  9. Click Continue.
  10. Repeat these steps for each scanner where you want to change the maximum message size.
  11. On the Host Configuration page, click Save.
  12. Confirm that you are able to accommodate your desired message size by sending a test message. If the test fails, repeat these steps and retest until you are able to receive your test message.

Additional information

  • Symantec recommends that you keep the "Maximum message size in bytes" setting uniform for both Inbound and Outbound, for each scanner in the Control Center. This prevents SMG from rejecting replies to messages and simplifies troubleshooting similar issues later.
  • Add approximately 20% to the number of bytes to allow for message body content and mail headers. This rule of thumb is a starting place for your testing and is not a guarantee of a particular threshold where this error will occur again.
  • After increasing "Maximum size in bytes," monitor SMG for impacts to performance and disk usage.
  • Use the proper conversion from megabytes to bytes, where 1 megabyte equals 1,048,576 bytes. For example, 20 GB would be 20,971,520 bytes. The default is 10 GB, which equals 10,485,760 bytes.