Joshua Baer, CTO of Datran and co-chair of the Email Sender and Provider Coalition's technology committee, offers a refreshingly simple analogy for authentication that I think most can grasp and take home. Baer likens email authentication to license plates on cars. The license plates themselves don't actually affect the way the car drives, but they create accountability that does affect the behavior of actual drivers.

"Before authentication, it was like there were no license plates on any of the cars. If a red Ford truck did something wrong, the spam police had to stop all the red Ford trucks. If you were in a red Ford truck, there was no way to make yourself look any different than the bad guy," explained Baer.

Put simply, authentication is the first step -- the foundation -- of tying your email message indisputably to a real world entity -- in this case, the credit card that was used to purchase the domain name. Authentication itself doesn't stop spam. In fact, we expect spammers and viruses to employ email authentication. But it's much easier to control spam and build "email reputation" in a world where most of the mail is authenticated than if it's not.

In 2006, email authentication was encouraged by ISPs such as MSN Hotmail and Yahoo and by almost all email trade association,s including the ESPC, MAAWG, and the DMA. Many senders authenticated to help add momentum and show their innovative leadership. In 2007, email authentication will be required for anyone sending legitimate email.

The cost of not employing both SenderID / SPF and Domain Keys (DKIM) is significant now and growing. Unauthenticated email is more likely to get put in the spam folder or rejected outright by major ISPs such as MSN Hotmail, and by thousands of corporate Exchange servers. Most new white lists and feedback loops are only available for authenticated mail. It is quickly becoming impossible to achieve optimal delivery without both forms of email authentication.

If you are interested in learning more about authentication, www.deliverability.com and the Authentication and Online Trust Alliance are great resources, as is the Interactive Advertising Bureau. where Baer led the development of a few deliverability-, accreditation- and reputation-related works.

You may be interested attending the upcoming AOTA Summit, April 18-19, or you can catch up with some of the leading email marketers at the OMMA Hollywood Conference March 19-20.

This commentary is insightful. I recommend it to others.