Starting Symantec Messaging Gateway (SMG) version 9.0.x, the appliance is detecting and acting on emails carrying the winmail.dat file.

The winmail.dat file is a binary attachment and is detected by SMG as Transport Neutral Encapsulation Format (TNEF) file type. The TNEF file type is part of the Archive Files attachment list on SMG.

If SMG has been configured to act on archive files, messages containing the winmail.dat are expected to match this policy. The result is whatever action has been configured on the matching policy.

The file is properly detected as an archive file (TNEF) by SMG and the result is what the policy to match archive files has been configured to do.

The administrator can remove the TNEF file type from the Archive Files list but that would also prevent other TNEF files from being detected.

The following articles provide more information on this file and how to prevent the generation of them:

How e-mail message formats affect Internet e-mail messages in Outlook

http://support.microsoft.com/kb/290809

How to Prevent the Winmail.dat File from Being Sent to Internet Users

http://support.microsoft.com/kb/138053

Applies To

SMG is accepting messages that contain an attachment called winmail.dat. This file is generated by some Microsoft products like Outlook and Exchange.