Here's a story I missed when it broke. On March 25, Microsoft was awarded a patent it applied for nearly 4 years ago, to fight search spam based on external elements, like "electronic documents," or email. The prevailing theory is that similar indicators will show up in spammy emails and spammy blog comments and other SEO spam.
Given the resurgence of spam from SEO companies, Microsoft may also want to use the spam filters built into Outlook to highlight potential SEO spammers, working on the theory that spammers are spammers, in any and all fields. No question that this approach may be susceptible to some level of abuse, but given the amount of people using Office, it's unlikely that subscribing your competitor's newsletter and then tagging it as spam will really affect them. SeoByTheSea wants to take it even further, and suggests that the URLs in spam emails get tagged as SEO spam as well.
But before we get all that excited about what direction Microsoft (or MicroHoo) can take this innovation, we need to remember how poorly Microsoft has used this to deal with SEO spam in the past 4 years. A Google or MSN group with any keyword in the title will still rise, almost automatically, to the top of Live.com SERPs, regardless of its relevance. Let Microsoft fix that loophole first, and then go after email/SEO spam convergence.