Microsoft Forefront Online Protection for Exchange - subscription license (

Microsoft Forefront Online Security for Exchange is a hosted service for inbound and outbound e-mail that provides corporations with a frontline defense against e-mail-borne malicious software. It is a fully hosted solution that provides inbound and outbound messaging protection and management services to enterprises worldwide and gives e-mail administrators an effective way to enforce policy on e-mail use. With a simple configuration change to the Domain Name System (DNS), you can begin using Forefront right away.