The first half or so of my backlogged emails took all of an hour to delete, mostly a matter of determining I could have deleted them ages ago and doing so. I suspect the lesson here is to get better at deleting email when it arrives.
I expect the next quarter of them to take more work, because they require writing actual responses.
The last quarter take the longest, though, because those will be the ones that require me to actually do something, or finish something. I fear finding out how many of last quarter have been in my inbox since the last time I cleaned out my inbox.
What strategies do you all use to keep on top of your email?