Microsoft is pushing its own email Caller ID system. The idea is to prevent email address forgery, and hence reduce spam, by verifying that an SMTP server that is trying to send email for a domain (like plasticboy.com) has permission from the domain owner to send email for that domain. Currently, anyone can send email claiming to be from any domain. Microsoft's system is very similar to Sender Policy Framework, which has been submitted to the IETF as an Internet-Draft.