Inbox One, the pragmatic approach
The Getting Things Done methodology encourages behavior such as Inbox Zero, the concept of dealing with all the items in your inbox and keeping a zero count. In previous jobs, I've tried to do this, and struggled at times, having as many as 1000 items. Even when triaging my inbox regularly, I'd still end up with 50 items that needed some sort of attention.
Lately, I've been using Gmail for personal and work email, and have found a balance that isn't as stringent as inbox zero, but eliminates most of the mail. I call it Inbox One, as in one page of email. At any given time, I have at most enough email to fit on one page. As soon as it gets larger than a page (or I get a downturn in work), I clean it out as much as I can.
Currently, I have 3 items in my work inbox (up 50% from this morning, oh no!) and 10 items in my personal email inbox. Only 1 of those 13 items need attention today.
I still follow the Inbox Zero teachings, but try to be a little more pragmatic. Not everything needs to be handled immediately, but as much that can be dealt with quickly, or properly scheduled as work to do in the near future, I take care of. What is left are a few items that eventually need to get done. Like Inbox Zero, anything unimportant is archived, deleted, or filtered.
Inbox Zero is near impossible to maintain all the time unless you are very self-disciplined. Inbox One is far more tenable.