This reports whether Anti-Virus scanning of SMTP, meaning email, traffic specifically is currently enabled on this gateway. Since email attachments remain one of the most common malware delivery vectors, this state is one an admin should treat as critical to keep enabled: if disabled, malicious attachments would pass through to mail servers behind the gateway unscanned even while HTTP and FTP scanning continue normally. For example, this reading Inactive after an unrelated mail-relay performance tweak would leave all inbound email attachments unscanned until corrected.