A Colorado man who was charged with sending hundreds of thousands of spam e-mails has been sentenced to 21 months in prison after pleading guilty to tax evasion and fiddling with e-mail headers.

Edward "Eddie" Davidson, 35, of Louisville was also ordered to pay $715,000 to the Internal Revenue Service. Davidson used false e-mail headers to disguise the sender. The spam was meant to dupe stock investors and manipulate markets.

He made about $3.5 million sending e-mails for nearly 20 companies.