virswall 6.2 configure question

Now i have configure viruswall for linux for scanning incoming and outgoing
message. the structure as below.

* In and out message same viruswall machine.

in ----> viruswall 6.2 for linux ---->exchange server
out <----viuswall 6.2 for linux <----exchange server

My question as below

** viruswall for linux as different with for windows version.
** How setup incoming message scaned by viruswall after forward to exchange
server? is using sendmail configure , pleasea advice.
** incoming message using SMTP 25 , forward to external SMTP using Port 25,
how to configure. please advice.

I hope can solve my problems. Becuase i need implement this solution to our
network .

Thx
IT