I'm not sure why this didn't occur to me before... I read recently another brief article about the negative impact of email on productivity the other day, so I was thinking about a way to deal with it that didn't involve, e.g., closing Outlook and maybe even setting an "I'm not available by email until 3p today" out of office type message--seems a bit extreme, and it would also preclude my getting meeting reminders.
It occurred to me that what usually happens is I get the nifty little toaster popup notification while doing something, almost always click on it for more detail, and then get drawn into a distraction over it. Similarly, I was using one of those Gmail Vista gadgets that would highlight when I had Gmail waiting, or I'd leave it open and minimized and see the Inbox count in the taskbar. The problem was not (for me) so much getting too much email as having the regular interruptions that were occasioned by these terribly useful notification mechanisms.
Having isolated the problem, i.e., having framed the question correctly (which usually the most important part of solving a problem), I asked "How can I make these notifications go away?" And the answer was immediately apparent: turn them off. :)
To that end, I went into Outlook advanced email options (Tools -> Options -> Email Options -> Advanced Email Options--who knew notifications were advanced?!) and deselect all the notification options:
I then removed the Gmail notifier gadget, and I close my Gmail when done with it. The magic is that I still get my task and meeting reminders, but I don't get the regular interruptive notifications. This had an immediate noticeable effect--I could work through to a good stopping point on the thing I was working on, i.e., a point I'd normally take a break, and then I'd check my email. Wow! Who knew something so simple could make such a difference? I figure if it is critical, somebody will call or come knocking on my door. :)
As a complimentary technique to that, I have taken my Inbox strategy to the next level, following a bit of advice given by Mark Hurst (who wrote a book on Bit Literacy [that I haven't read]). One of his suggestions to avoid information overload is to keep your Inbox empty. I previously already worked to do that because I used my Inbox like a to-do list (and don't like having a long to-do list), but Mark's advice is precisely not to do that--use it as an Inbox and get stuff out of it immediately.
Having not read the book (in which I'm sure are tons of helpful little tidbits), I take that to mean act on it immediately if possible, file it if need be, or set up a task to do something with it later. I was already doing the first two, but I've found this additional third technique to be a nice add. There is a distinct satisfaction (for me anyway) to having an empty inbox--maybe it's my personality type. :)
I hope this maybe helps others out there in the same boat.