This article applies to:

• Trustwave MailMarshal (SEG) 

Question:

• Why does MailMarshal SMTP not remove recipients from the email when flagged by DHA?

Information:

• In some earlier versions of MailMarshal SMTP, each recipient found to be invalid by the anti-DHA facility is stripped and a SMTP response 555 invalid recipient is returned to the sending server. This behavior reduces the load on internal email servers and reduces NDR sending, but it does not accomplish the task of DHA protection.
• In current supported versions, no response is sent until the configured limit is reached. When the limit is reached MailMarshal sends 556 Too many invalid recipient requests. Closing connection.
• In current supported versions, by default anti-DHA does not strip recipients.

A registry setting is available to permit the invalid recipient information to be stripped.

To configure stripping of invalid recipients by anti-DHA:

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 solved. Make sure that you backup your Registry prior to making any changes.

• In MailMarshal 10.0 and above, open the Management Console and navigate to Advanced Settings. Add a new value:
  • Name: Receiver.DHA.StripInvalidRecipients
  • Type: Boolean
  • Value: True (selected)
• In MailMarshal 8.X and below, open the Registry Editor on the Array Manager. Within the base registry key, navigate to \Default\Receiver\DHA
  • In version 8.X: HKEY_LOCAL_MACHINE\SOFTWARE\Trustwave\Secure Email Gateway\Default\Receiver\DHA
  • For information about the registry location for each version, see article Q10832.
  • Enter the value as a new DWORD value named StripInvalidRecipients with value 1.
• Save your registry settings or configuration settings.
• Commit the configuration changes and restart the MailMarshal Receiver service on each node.