Microsoft is suing Connecticut-based spammer Boris Mizhen for sending unsolicited email to millions of users on its Hotmail web-based email sevice.
The software giant has accused three companies allegedly controlled by Mizhen - Media Network, Inc, New Age Opt-In, Inc and Permission Inc - of duping Hotmail into believing that the spam email messages sent by the firms were legitimate mail.
Hotmail uses filtering technology to distinguish between legitimate email and spam, automatically redirecting unsolicited mail into junk mail folders.
This is the second time the spammer has been sued by Microsoft - an earlier lawsuit in 2003 resulted in Mizhen having to pay Hotmail's owner $2 million and promising never to send spam e-mail to Hotmail users ever again.
Online Media Daily explains that in the current case, Microsoft accuses Mizhen of manipulating Hotmail spam filters by creating up to 200,000 bogus Hotmail accounts and using them to move messages sent by the companies from junk mail folders into their inboxes, fooling Hotmail's filters into believing that they were legitimate.