There is no need for us to provide anti-virus on a Linux box. We manage those, and our security team will handle the server threats.
We can provide anti-virus on Windows boxes. We will install it for free, but there is none installed by default other than the Mail virus scanner.
There is no need to provide anti-virus for email. People already handle virus threats on their PC's. Extra virus protection would just mean more waiting for you while the same scan is done twice.