America Online Inc, the world's largest Internet service provider, has agreed to buy privately held Mailblocks Inc, developer of a service designed to block junk e-mail, AOL said on Wednesday.
Terms of the deal were not disclosed.
The Mailblocks service uses a patented "challenge/response" technology to block unrecognised junk e-mail while allowing legitimate senders' e-mail messages to pass through to recipients.
Such systems involve a two-step process in which all incoming messages are initially blocked until the recipient recognises the sender as an acceptable correspondent. In effect, the system works by building up an address book of accepted e-mail addresses while blocking unrecognised senders.
Mailblocks has emerged from a highly fragmented field as one of the leading services for blocking unwanted e-mail, or spam. Scores of companies offer various approaches, none of which offers a "silver bullet" for halting the spam deluge.
Mailblocks, based in Los Altos, California, was founded in 2002 by Phil Goldman, a co-founder of WebTV, a television-based Internet access service for computer neophytes. Goldman died last year.
Mailblocks was commercially launched in March 2003 as an e-mail service for both home users and small businesses.
America Online, a unit of Time Warner Inc, said its purchase of Mailblocks is the latest demonstration of its commitment to confronting the spam scourge, which has become a plague on e-mail users around the world.
AOL, together with other major Internet companies such as Yahoo! and Microsoft, have struggled for the past two years to redesign their e-mail systems to help users manage the daily glut of spam.
Because many of these efforts rely on changes in consumer behaviour and some technical sophistication, frustration with spam continues to mount.
The Internet industry has also worked with police and offered bounties to help identify and arrest major spam distributors.
AOL members will begin to see Mailblocks technology introduced through a series of phased upgrades in the near future, AOL said. It will be available as an option within the AOL service's spam-control menu and for users of its Web-based e-mail service.
AOL said a transition plan is being developed for current users of the Mailblocks service, who may continue to use the full features and functionality of Mailblocks for an unspecified amount of time.