This article applies to:

• Trustwave MailMarshal (SEG)

Question:

• How do I limit the size of an incoming message?
• How do I have SEG 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:

1. On the Array Manager, edit the Registry (10.X: use Advanced Settings in the Management Console)
2. Navigate to the SEG Receiver key:
   • In version 8.X: HKEY_LOCAL_MACHINE\SOFTWARE\Trustwave\Secure Email Gateway\Default\Receiver
   • 10.X: value names have the prefix Receiver. (Receiver dot).
   • For full details of the location for each product version, see article Q10832.
3. Create a new DWORD (integer) value called MaxMessageSize
4. Set the value of the new DWORD value to the desired value in BYTES (Decimal).
   • Warning: Do not enter a value larger than 2GB (2 000 000 000).
5. Commit configuration changes.
6. Restart the MailMarshal Receiver service.

Now if an incoming message exceeds the configured message size SEG 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, SEG will reject the message immediately.
• SEG 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