[ctdonath]

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.

[julian37]

do some probabilistic sorting for me!

Gmail's Priority Inbox does this, and it works reasonably well. https://support.google.com/mail/answer/186531?hl=en

if sender (&/| reply-to) has never been seen before, shove it to the other end

That would only be helpful in a world where you never make new contacts.

[dmbaggett]

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.