According to Stefan Pollard, last week's Authentication and Online Trust Alliance Summit in Boston clearly showed authentication is an integral tool in the fight against spam and e-mail fraud -- and is being widely adopted by senders and receivers alike.
The summit also made clear that authentication alone is not enough. You must have a solid sender reputation.
ISPs use reputation to determine not only the legitimacy of incoming mail, but also whether it's wanted by and relevant to recipients. E-mail delivery statistics will get a lift with authentication, but the full benefit is delivered only when a good reputation backs you up.
To borrow the analogy used at the conference: "Think of authentication as your driver's license and reputation as your driver's record." The ISP may know who you are, but if your driving record stinks because of arrests or fines, the delivery cops won't allow your e-mail into the inbox.
In several case studies, Microsoft showed how it uses reputation data to supersede or override content filters that could block or filter messages. Mail that scored poorly for content actually got routed to the inbox because the sender's reputation score was more heavily weighted than the content score.
Conversely, a whistle-clean e-mail message can get stopped cold or filtered if it comes from a sender with a poor reputation score.