Typically all you will see from the SMG aside from the host header information is the x-brightmail-tracker and possibly others if you have CF rules configured to add other x-headers.
A quick google search shows these may be added by Symantec Endpoint Protection.
http://www-10.lotus.com/ldd/nd85forum.nsf/R2R+Print?OpenForm&ParentUNID=6E9DEB763B5D575985257A3A002859F5