Need a solution to implement a antivirus smtp gateway

Hi

We want to use Exim and Exiscan to implement an smtp gateway
(external.company.com) that will receive any mail with adresses like
user@external.company.com, scan against viruses and spam the mail, and
if everything is ok, resend this mail to user@internal.company.com. Mail
are definitively stored in the internal.company.com.

I would like to know if it is possible ? And if yes, does somebody have
some configuration files of the external server to help the system staff
to implement that rapidely.

Regards,

Thierry