Microsoft this week dropped McAfee virus protection technologies from its Hotmail Web-based email service and replaced it with a solution from McAfee competitor Trend Micro. With 187 million active users, Hotmail is a huge coup for Trend Micro, which is already touting the deal in online and periodical-based advertisements. Neither Microsoft nor McAfee has issued an explanation for the change. Terms of the deal with Trend Micro have not been revealed.

"MSN is focused on providing a safer online experience for consumers, and we continue to make investments in this area," says Microsoft Director of MSN Communication Services Phil Holden. We're pleased to work with Trend Micro, with its deep antivirus expertise, to expand the email protection of our Hotmail customers. Today MSN Hotmail is the only free global email service that provides antivirus scanning and cleaning for its customers. We see this offering as important in helping protect our Hotmail customers while also guarding members of the overall Hotmail community and the friends and family they email."

Under terms of the deal, Microsoft will utilize Trend Micro's anti-virus technology to scan both inbound and outbound email messages and attachments that travel through Hotmail's massive email system. The software will run on Microsoft's MSN servers and will link to back-end Trend Micro virus definition servers. Previously, that service had been provided by McAfee, which first signed up with the software giant in 1998. According to Trend, its retail package PC-cillin Internet Security 2005, includes the same anti-virus technology that Hotmail is now using.

Trend Micro is currently the world's third-largest supplier of anti-virus solutions, behind Symantec and McAfee, both of whom remain large Microsoft partners. Trend hopes that the Hotmail alliance will help spur further sales of its consumer-oriented products.