lithorn writes "A start-up named MailBlocks owns two patents which claim processes that to protect an email account from receiving spam by using a whitelist. Mail from addresses not on the whitelist receive a challenge email in reply; the sender must then reply to the challenge to prove that there is a human on the other end.
EarthLink, this country's third-largest ISP, announced a similar new service this week, except that the sender must type information into a web page.
MailBlocks lost no time in suing EarthLink. It has already sued three other companies, but this suit has a higher profile due to the size of EarthLink's customer base.
The New York Times has the story here."