(FORTUNE Magazine) – YOU PROBABLY DON'T KNOW SCOTT Richter, but there's a good chance you've gotten e-mail from him. Once ranked the world's third-largest spammer, he is estimated to have sent 250 million unsolicited e-mails a day. Subject lines that read "Mortgage! Low! $$$! Now!" or "Herbal Vi@agra Firesales" are supposedly some of his favorites. Richter's company, OptInRealBig.com, doubled its profits to $19.6 million last year, and in the first quarter of 2005 it had already earned $11.4 million (Richter took home a $1.2 million paycheck last year). But in March both Richter and his company were forced into bankruptcy. And there's one man he blames: Bill Gates.

Spam now accounts for 79% of all e-mail traffic, and "Bill gets a lot of spam," says Aaron Kornblum, Internet safety attorney for Microsoft. "Getting rid of it all is a passion for him."

Richter was a fat target. By the time he graduated from high school he had already earned some $500,000 from various ventures, including candy sales and videogame operations, according to Brian McWilliams, author of Spam Kings: The Real Story Behind the High-Rolling Hucksters Pushing Porn, Pills, and @*#?% Enlargements. At 21, he became the youngest person in Colorado to ever hold a liquor license. After founding his spam empire in 2000, he quickly became known as "Snotty Scotty" for taunting those who hated him most. A few years ago, for instance, he popped up in an online anti-spam forum, where he wrote, "I love the public's eye and attention. I LOVE EVERY MINUTE OF IT. MAKE ME FAMOUS." At one point he even tried to launch a line of Spam King hats and T-shirts.

Then, a week before Christmas in 2003, Microsoft teamed up with New York attorney general Eliot Spitzer and sued OptInRealBig.com for more than $40 million, calling its practices illegal under that year's new CAN-SPAM law. "There's nothing we can do when a company has $80 billion in the bank and wants to put their competition out of business," Richter wrote FORTUNE in an e-mail. Following the advice of counsel (his father, specifically), Richter declined to discuss the case further. Before hanging up the phone, however, he insisted that OptInRealBig.com will stay in business and that he will countersue Microsoft.

Whether or not Richter survives, "this is a big deal," says Jim Nail, principal analyst with Forrester Research. "Richter was one of the few public faces of spam." Microsoft, however, already has its sights set on other targets, says Kornblum. The company has filed 135 lawsuits worldwide, including suits against 215 different spammers and an additional 117 lawsuits against e-mail fraudsters called phishers. The next big target: Ryan Pitylak, a junior at the University of Texas whom Microsoft and the Texas attorney general are suing. According to the attorney general, the 22-year-old owns a $450,000 house in one of Austin's nicest neighborhoods, keeps a Jaguar parked in the driveway, and is believed to be the fourth-biggest spammer in the world. -- Cora Daniels