AOL is endorsing a sort-of authentication system for email (much like caller id) that is based on an emerging standard called, "SPF." Learn more here.
Quoting:
Posted by ejnorlin at January 22, 2004 08:22 AM
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.