Peter Francis-Macrae's sentencing on Wednesday in the Peterborough Crown Court followed his six-week trial and his conviction on charges of fraudulent trading, concealing criminal property, threatening to destroy or damage property, making death threats, and blackmail.
Francis-Macrae of Cambridgeshire was accused of defrauding thousands of people by tricking them into sending him money to register an .eu domain name on their behalf. He was also charged with sending fraudulent e-mails to companies and claiming they had to pay a renewal fee to avoid losing their domain names.
It has been estimated that Francis-Macrae received up to $2.8 million (1.6 million pounds) through the scams.
Businesses that complained said that Francis-Macrae bombarded them with e-mails. Police and trading standards officers who investigated told the court that they were threatened with gasoline-bombing.
The jury also heard that Francis-Macrae ran the scam from his bedroom at his father's home in St. Neots, Cambridgeshire.
According to the London Times, Judge Nicholas Coleman told Francis-Macrae: "You deceived hundreds of people of countless thousands of pounds of their money. When investigated, following the countless complaints of your misdeeds, you resorted to threats to kill and a threat to set fire to property, and ultimately blackmail.
"Whoever stood in the way of your criminality became subject to abuse and threats. You are, I think, one of the most vindictive young men I have ever seen," Coleman added.
Spamhaus, a group that identifies spammers and helps Internet service providers block their traffic, includes Francis-Macrae on its list of professional spammers.
Francis-Macrae was arrested after threatening Nominet UK, the registry that controls the .uk domain.
Nominet UK had warned businesses not to fall for the bogus invoices being sent by Francis-Macrae. He responded by phoning Nominet and threatening to attack its systems with a botnet of 200,000 zombie PCs unless the warning was withdrawn.
Francis-Macrae has also been accused of sending a spam e-mail in 2003 that told people they were about to be billed nearly $700 unless they called a telephone number to cancel the order. The number belonged to Cambridgeshire Police, who had recently arrested Francis-Macrae, and the attack jammed the police force's network.
Graeme Wearden of ZDNet UK reported from London.