You can keep your Inbox clean and clear when you delete every message as soon as you do not need it any more. But are you sure you don't need it any more?
You certainly don't want an Inbox containing several hundred or even thousands of messages, though. This doesn't help remembering either as it becomes increasingly difficult to retrieve old, "archived" messages.
Filing, but Where?
Filing messages is supposed to be the solution to the problem. But where should you file them?
I have tried a number of mailbox layouts. Most suffer from various of difficulties. Either it is difficult to decide what mailbox a certain message belongs to (often it is more than one, sometimes none) or finding archived messages becomes a guessing game.
Mailboxes for People, Mailboxes for Topics
The difficulties can never be eliminated completely, but I think they can be minimized by a mailbox setup that combines mailboxes for people and mailboxes for topics. From the two, mailboxes for people take some precedence because they are the stronger concept.
Every message you get has a sender. Most senders belong to one of a certain set of groups. The message comes from a mailing list, from coworkers, from family members, from friends, or from strangers. This is exactly what your initial mailbox layout should look like:
- one mailbox for every mailing list you are on,
- one for coworkers,
- one for your boss maybe,
- one for the family,
- one for friends, and
- one for people you do not know yet.
Everything Fits
You'll find that most messages you receive or send fit in exactly one of these mailboxes. If a single person is particularly important or generates a lot of message volume, they get a dedicated mailbox.
While setting up individual mailboxes for mailing lists is useful, it makes no sense to have a special folder for every newsletter. That's where the mailboxes dedicated to topics can help. Depending on your interests, you'll have a mailbox for health newsletters, one for sailing newsletters, one for philosophy newsletters, or whatever.
If you are not using your Inbox as the to do list folder, you can set up a special to do folder. And you can create topical mailboxes ad hoc. For example, you can set up a mailbox for a project. In that mailbox you collect the messages that you constantly need for reference while you work on the project. When the project is done, so is your ad hoc topical mailbox and you can move its messages back to their original mailboxes.

