Here's a thought to toss out and see if it sticks (or has been done):
How about an email app which groups messages by frequency/familiarity of sender? If someone sends me messages often, or has sent stuff on occasion over a very long time, group it at one end of the inbox; if seldom and not known for long, somewhere in the middle; if sender (&/| reply-to) has never been seen before, shove it to the other end. Maybe also track how long I read their messages: if I spend time on what's sent (relative to content size), it's important; if it's straight to trash or less than a half-second, put it in the "junk to screen" pile. VIP/white/black-lists are a pain because I have to screen every address listed; do some probabilistic sorting for me! don't just list things in a linear or threaded by-receipt-date line.
Inky (http://inky.com) already lets you sort by relevance. It's much more useful than VIP/whitelist/blacklist but we're continuing to play with the relevance metric to further improve it. It does take sender frequency into account.
How about an email app which groups messages by frequency/familiarity of sender? If someone sends me messages often, or has sent stuff on occasion over a very long time, group it at one end of the inbox; if seldom and not known for long, somewhere in the middle; if sender (&/| reply-to) has never been seen before, shove it to the other end. Maybe also track how long I read their messages: if I spend time on what's sent (relative to content size), it's important; if it's straight to trash or less than a half-second, put it in the "junk to screen" pile. VIP/white/black-lists are a pain because I have to screen every address listed; do some probabilistic sorting for me! don't just list things in a linear or threaded by-receipt-date line.