A man has been sentenced to nine years in jail by a Virginia judge for sending millions of junk emails, or "spamming".
Jaynes remains free while his case is being appealed
Jeremy Jaynes, 30, is the first person in the US to get a prison term under a spam law. He is said to have been the world's eighth most prolific spammer.
By selling sham products and services advertised in his messages, he earned up to $750,000 (£398,000) per month.
Jaynes has appealed, and the court has put off the start of his prison term because the new law raises questions.
Under Virginia law, sending bulk email using fake addresses is a crime.
"It was not just sending bulk emails, he was falsifying the routing information, disguising the origin," said prosecutor Lisa Hicks Thomas.
"The end user couldn't say: don't send this to me," she added.
Ms Thomas said she was pleased with the ruling and hoped it would be upheld.
Jaynes was operating through an America Online (AOL) server in Loudoun County, where the world's largest Internet services provider is based, and is believed to have sent some 10m unwanted emails a day.
Products advertised in his emails included a "Fed-Ex refund processor" which he claimed would have allowed people to earn $75 an hour by working from home.
Jaynes, who is from North Carolina, will appeal on the grounds that he has been charged as an out-of-state resident under a Virginia law that has only just come into effect.
His sentence is the harshest punishment handed down so far for junk emailing in the US, and appears to be a strong signal that authorities will not tolerate the spamming business.
Jaynes has pledged that regardless of the final outcome of his trial, he will never again be involved in what he called the "email marketing business".
It is believed that 70% of all emails are spam.