Clay Shirky, author of the book “Here Comes Everybody: The Power of Organizing Without Organizations,” believes that “we don’t have information overload; we have filter failure.” I completely agree with this, but creating filters can become a chore too. My solution would add a single-click button called Auto Filter. Once pressed, it would do its best to analyze the message and create a new filter, and then file future messages into this new category.
Presumably the filters would only need to be new when you first started using the feature: after a short time the app would start adding new messages to already existing filters. (Otherwise you’d have a new filter for every message.) Another possibility would be to set up some filters manually at the beginning, and ask the app to try to fit new messages into one of the existing filters, only creating a new one if it can’t find any plausible matches.
This is one step beyond Gmail’s already excellent filtering system, which works only on the basis of criteria you explicitly set up. (The “smart folders” used in Mac OS X’s Mail application, and elsewhere in the system, are exactly the same thing: saved searches.) All that said, this is the kind of thing that should only be used by people who get email in enormous volume, because it’s a recipe for shunting messages into folders that you never look at.
I expect Gmail to offer something like this before too long. A number of desktop apps do this kind of automatic sorting already: my “everything Bucket,” Together offers the option to auto-tag new files based on existing tags — though in my experience it doesn't do this very well — and many people are devoted to DEVONthink because of its “Artificial Intelligence,” that is, its ability to sort and auto-classify large numbers of documents. I think addressing “filter failure” will be a major goal of many kinds of software in the coming years, and I expect Google to lead the way in this endeavor.
One more thing: How long will people be worrying about an “email glut”? Already many people use email only for business purposes, having redirected their personal communications to Facebook and Twitter. My teenage son, for instance, gets and sends absolutely zero personal emails. When email is a place for business and business only, some important filtering has been done.