Hello!
Do you mean these products:
Symantec Brightmail Message Filter 6.x
-> this is running as an SMTP Gateway
Symantec Brightmail Gateway 7.x / 8.x (formerly Mail Security 8300 Series)
-> in in my opinion the successor of "Symantec Brightmail Message Filter"
-> this is running as an SMTP Gateway
Symantec Mail Security 6.x for Microsoft Exchange (SMS for Exchange)
-> used in addition to Exchange 2000/2003/2007
Regards
Frank