Is there any way to limit Mail Size at the Receiver for both SMTP and ESMTP?

This article applies to:

• Trustwave MailMarshal (SEG)

Question:

• How do I limit the size of an incoming message?
• How do I have MailMarshal block incoming messages based on a size limit?

Reply:

You may be able to limit message size with a Receiver Rule. However this method depends on ESMTP and only works if the sending server provides an accurate size, which is optional.

You can set a hard limit that will apply for both SMTP and ESMTP connections. To set the limit, use the following registry setting:

• In MailMarshal 10.0 and above, open the Management Console and navigate to Advanced Settings. Add a new value:
  • Name: Receiver.MaxMessageSize
  • Type: Integer
  • Value: The desired message size in bytes. The maximum allowed value is 2GB (2 000 000 000).
• In MailMarshal 8.X and below, open the Registry Editor on the Array Manager. Within the base registry key, navigate to \Default\Receiver
  • In version 8.X: HKEY_LOCAL_MACHINE\SOFTWARE\Trustwave\Secure Email Gateway\Default\Receiver
  • For information about the registry location for each version, see article Q10832.
  • Enter the value as a new DWORD value named MaxMessageSize (size in bytes). Use Decimal numbers to avoid confusion. The maximum allowed value is 2GB (2 000 000 000).
• Save your registry settings or configuration settings.
• Commit the configuration changes and restart the MailMarshal Receiver service on each node.

Now if an incoming message exceeds the configured message size MailMarshal will return the message "552 Message exceeds fixed maximum message size."

This registry entry sets a limit on the receipt of SMTP and ESMTP messages.

• If the other server provides an ESMTP SIZE value greater than the limit, MailMarshal will reject the message immediately.
• MailMarshal will also reject the message if the data actually received exceeds the limit. This action does not depend on ESMTP.
• This setting does not have a default value. The limit only applies if a value has been entered and committed.

Notes:

Warning: Using the Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Trustwave cannot guarantee that problems resulting from the incorrect use of Registry Editor can be resolved. Make sure that you back up your Registry prior to making any changes.

This article was previously published as:

NETIQKB43176