This article applies to:

• Trustwave MailMarshal (SEG)

Question:

• How does MailMarshal handle messages that have a header line longer than 998 characters?
• Can MailMarshal repair header lines that are longer than the RFC maximum of 998 characters?

Information:

Internet RFCs set a maximum of 998 characters for SMTP header lines. Some servers (and most email clients) ignore this standard.

• In supported versions of MailMarshal, by default these messages are fixed by "folding" the offending headers onto multiple lines as specified in the RFC. This action should ensure that all compliant SMTP software accepts these messages.
• You can choose not to change the headers.

Procedure:

To disable folding of long header lines:

• In MailMarshal 10.0 and above, open the Management Console and navigate to Advanced Settings. Add a new value:
  • Name: Receiver.FoldLongHeaders
  • Type: Boolean
  • Value: False (unselected) to stop the default "folding" behavior
• 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 FoldLongHeaders with a value of 0 to stop the default "folding" behavior.
• Save your registry settings or configuration settings.
• Commit the configuration changes and restart the MailMarshal Engine service on each node.

As always, take due care when editing the Registry. Trustwave recommends that you make a backup before making any changes.