SEATTLE -- A man defrauding people through tens of millions of spam e-mail messages sent around the world was sentenced Tuesday to just under four years in prison.

Prosecutors had asked that Robert Soloway - dubbed the "Spam King" by federal investigators - be sentenced to years, but the judge said available sentencing guidelines made it difficult.

Judge Marsha Pechman said laws governing spam are very new territory for the courts, and the CAN-SPAM Act allows for only a maximum sentence of five years.

"It's very difficult to assess that loss with specificity," said prosecutor Kathryn Warma. "That is why the judge appropriately based the loss on the amount that he made through his criminal enterprise."

Federal prosecutors allege that from November 2003 to May 2007, Soloway sent tens of millions of e-mail messages to advertise his company, which offered software to send out broadcast e-mails. For $495 customers could have an ad sent to 20,000,000 e-mails, or receive software allowing them to send up to 80,000,000 e-mails.

He continued to send the junk e-mail even after Microsoft won a $7 million civil judgment against him in 2005 and the operator of a small Internet service provider in Oklahoma won a $10 million judgment.

Soloway, 28, sent out unsolicited bulk e-mails using networks of compromised computers called "zombies." These are generally home computers whose owners typically have no idea that their machines have been infected with viruses or other malicious programs; service providers can't easily block messages from zombies because they are mixed in with legitimate messages.

"I take full responsibility for this. I sent out a lot of spam," Soloway said in court.

He refused to elaborate on just how much spam he sent out, but he said he doesn't believe he's the Spam King.

"I'm not going to say I'm innocent, and I'm not going to say its the government's fault. It's fully my responsibility and what I did was not right," he said.

In a plea deal with the U.S. Attorney's Office, Soloway pleaded guilty to mail fraud, fraud in electronic mail and failing to file a tax return.

Prosecutors rejected Soloway's offer to help reduce spam as a part of the deal.

"I knew people that could cut spam (by) 50 percent. The prosecution essentially said, 'we don't care, we want you to go to prison as long as possible,'" said Soloway.

Soloway is one of the first defendants in the country to be convicted of criminal spamming. Court documents say Soloway was "brazen and even boastful that he is above the law and anyone - including federal judges."

In court on Tuesday, Pechman likened Soloway to an 11-year-old boy who sat down at a computer years ago and never grew up.

When his sentence was announced, Soloway simply smiled.

In addition to the 47-month sentence, Soloway will have to pay $700,004 in restitution for the profits he made from his spam operation.

"The government wanted to make an example of me and they did it," he said.

He is expected to begin serving his sentence in 60 days, and Pechman allowed him to remain free until he reports to serve his time.