'Spam king' Robert Soloway has been sentenced to 47 months in prison.

US resident Soloway, who sent millions of unsolicited emails, pleaded guilty to fraud, spamming and tax evasion after being indicted in May 2007. It emerged that Soloway continued to spam even though he previously lost cases brought against him by Microsoft and a US ISP.

Assistant US attorney Kathryn Warma said during the trial: "A disturbing theme we repeatedly saw from the complainant is, why isn't the law being enforced on the Net? Why isn't CAN-SPAM being enforced?"

Judge Marsha Pechman, who sentenced Soloway, hoped the sentence will serve as a warning to other online criminals and suggested guidelines regarding sentencing for online crimes should be written.

"This statute really needs a set of guidelines written and tailored to the CAN-SPAM act, tailored to the evolving computer science that allows people to engage in this activity. The current guidelines are not really very helpful, especially when CAN-SPAM violations are combined with other crimes," she said.

The Soloway case is one of very few spam crimes that have been bought to court. Among those successfully tried recently are Jeremy Jaynes who was given nine years imprisonment and Adam Vitale who got just over two years after being convicted of spamming.

"None of those cases, not one, comes close to this case in terms of the duration of the maliciousness, the harassment techniques, the high level of spamming activity that we have in this case," Warma added.

See also: AOL spammer gets 30 months in prison