The idea of behavioral data affecting email sender reputation first surfaced three years ago, when AOL announced that dormant addresses would factor into sender reputation. AOL explained at the time that spammers create significant numbers of fake email addresses for the sole purpose of driving down complaint percentage rates. Even so, they said that this metric should never affect legitimate emailers who have genuine (human) email recipients.

The next phase of this concept was presented by Microsoft at the Authentication and Online Trust Alliance Conference in 2008 (PDF). Microsoft’s Anti-Spam General Manager indicated that in the future they would prefer to use recipient behavioral metrics like open-rates in addition to their other spam-related metrics to determine sender reputation. While the idea was still hypothetical at the time, the mere fact that they made these statements to a room full of email senders was worth noting.

Now, we have confirmation from Yahoo! that some of these same metrics that AOL and Microsoft have considered are now implemented into Yahoo!’s anti-spam reputation processes. Of course, we’ll never know exactly what percentage of non-openers or other behavioral factors will impact deliverability, but we can say with certainty that dormant addresses and inactive users are now playing a role in determining your Yahoo! inbox success.

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