Currently we send you a notification email if we reject a virus laden email sent to your account. There is a new option "Silently discard virus laden emails" on the Options -> Spam/Virus protection screen that allows you to just silently discard laden virus emails instead of being notified.

Additionally, virus laden emails with no "From" address, or a system "From" address (eg postmaster@ or mailer-daemon@) are always silently discarded as these are probably just bounces.