AOL tests caller ID for e-mail

America Online is testing an antispam filter intended to accurately trace the origin of e-mail messages, a move that could bring new accountability to the Net if it proves reliable

The online unit of media giant Time Warner last week implemented SPF, or Sender Permitted From, an emerging authentication protocol for preventing e-mail forgeries, or spoofing. The trial involves the company's 33 million subscribers worldwide and is the first large-scale test for the protocol, which standards groups are considering along with various other e-mail verification proposals.

Yahoo, AOL and other online service providers have been driven to act against spam because of its mounting toll on one of the most popular activities on the Internet--e-mail. More than 50 percent of e-mail sent today is unwanted junk, according to antispam companies, and the spam volume costs mail providers millions of dollars in hijacked bandwidth and storage, as well as defense measures.