Quck question: does any Symantec product protect PostFix email system (on Debian Linux)?
So, got the solution. Using Symantec Messaging Gateway may help (in my case it is part of SPS). Though SMG could not be installed on Debian - it could be placed as gateway on Symantec hardware or on VMware (e.g. on free ESXi) before mail server.
So, the case is closed. Whom should I ask to close this thread?