How I quickly process a lot of daily e-mail

Over 100 messages per day come to my email address. But most of them are just stuff to be filed and reviewed when it’s time to do the Roundup. Here’s how I process my email:
First, I filter out emails I know I can handle later (for the Roundup), leaving those that I’m more likely to need to deal with today. I use Gmail Rules to automatically process bulk mail into one of several categories:
News-Daily (newsletters that come daily, usually “this happened today” roundups about specific issues);
News-Weekly (longer-form articles, typically);
News-Monthly;
and News-RecommendLinks.
As part of the rule, I automatically mark these as read and archived so they don’t show up in my main inbox or on my phone clients.
For those that are left, I have three folders for messages that are for me:
1 – In
2 – Out
3 – Too Hard.
Once the bulk mail is automatically processed and out of the way, every day I go through emails in the morning and in the afternoon. If it’s a request I can deal with very quickly, I deal with it and move it to “Out” (e.g. done). Otherwise, if it’s got something specific for me to do, I move it to “In.”
Once the unprocessed mails are processed, I start going through the “In” folder and working my way through those emails in the time I have allotted for email. If I can get it done, I do it, then move it to “Out.” Some emails get moved to the “too hard” category – the request is out of the blue, for something that’s nearly impossible, or I got cc’d on something I shouldn’t have had. I move it to the “too hard” folder; if it doesn’t get referenced again, I don’t worry about it.
The beauty of this system is that it’s *simple*. I’ve tried to do topical assignments, but that takes too much time to think about – what topic does this message fall under? This system enables me to focus on what’s really important in email.