Mailblocks, a two-year-old California startup, was one of the highest-profile anti-spam companies that formed in the last few years. Its CEO and founder, Phil Goldman, who died last December, had previous success selling WebTV to Microsoft.

The company claims to have patents on the concept of challenge-response, a means of verifying that senders are seeing humans, with a visual puzzle, before allowing their email to reach its subscribers.

Mailblocks sued those companies, including EarthLink Inc, which it believed were infringing its patents. Some lawsuits are still outstanding, although court activity to date has not been promising that Mailblocks will succeed.

AOL spokesperson Nicholas Graham said the company has inherited the lawsuits, and will make a decision in the near future whether to pursue them or not. EarthLink, while a competitor, is a sometime ally when it comes to the spam issue.

Graham said that Mailblocks is known for having a slick user interface, and that AOL will use elements of that in its AOL and Netscape brand webmail services. The challenge-response features will be added at a later date.