Nam has posted a nice short review of ClearContext on his blog, The way of the geek. In it he talks a bit about our prioritization algorithm:
“How does it do the prioritziation of your mails you say? I don’t know the exact algorithm, but it learns over a period of time which people you deal with most frequently and places those at the top of your inbox. You can also manually set the priority of your contacts, so that people that you don’t hear from frequently, but are important, will still get placed near the top. Whether you are in the to or cc line will also affect the prioritization. In short, most of the stuff that needs your attention will get put at the top.”
This is fairly accurate. If you’re looking for a detailed description of how our prioritization algorithm works, check out our design whitepaper, Designing a More Effective Inbox. This thing is a little dated (check out that makehift logo!) but the core principles behind our prioritization algorithm haven’t changed.