Controlling "folding" of header lines longer than 998 characters

This article applies to:

• Trustwave SEG 7.5.0 and above

Question:

• How does SEG handle messages that have a header line longer than 998 characters?
• Can SEG 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.

• Versions of SEG and MailMarshal SMTP earlier than 7.5 relay such messages with no change in the headers.
• In SEG 7.5 and above, 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:

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. Add a DWORD (integer) value: FoldLongHeaders
4. Set the value data to 0
5. Commit configuration and then restart the Receiver service on each processing server.
6. To fold the headers, remove this value or set the data to 1.

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