I'm trying out SaneBox* as a way of managing my flood of email. It's a simple idea; that most email can wait for a while before it needs your attention. SaneBox places such messages in a folder called SaneLater and keeps them out of your inbox. It sends you a daily digest of these emails that you can read and delete/archive at leisure.
Sanebox works with any type of email platform, including corporate email 'solutions'. It uses algorithms to determine which emails truly are important, and in my trials of it so far, it is scarily effective, more so than Google's own Priority Inbox. My Inbox traffic has dropped by about 75%. One can also postpone emails to return to your inbox at a later date, a feature I haven't tried yet.
SaneBox is not free, which I do prefer, as it means it should stick around for a while.
Give it a try. It doesn't mess with your email at all, and if you don't like it after a free two week trial, SaneBox leaves without a trace. I signed up for a year after a week's trial.
*If you sign up through this link, we both get $5 free. If you don't want to be a part of helping to subsidise my blog, no hard feelings, just go to sanebox.com.