Highway's Virus Filter service endeavours to catch all email-sourced viruses, but cannot guarantee detection and removal of unknown viruses.
Highway still recommends that you have antivirus software installed on your computer for the purpose of detection, scanning and removal of known/unknown system viruses either pre-existing on your PC hard drive or ported to your hard drive from a non-email source.
Circumstances where viruses may escape Highway's scanning and detection system include but are not limited to, new viruses where software manufacturers have not yet issued signatures, as well as all situations of encrypted emails, which by their nature cannot be scanned.