Let me apologize in advance - I get quite strident about this sort of thing.
But you have to make sure that your folder tree is
squeaky clean and has exactly one bucket for each kind of email. -- Tristan
Ok, so I need your advice: where should I put the following emails:
1. From my wife about the next year vacation plan? @family? @vacation? @finance?
2. From my bank about credit for building my company's office? @finance? @bank? @business? @realestate?
I would ask you two questions: (1) Which of these categories has the most attention? (2) Where would you put the item, if it came on paper? -- Tristan
I assume TesTeq's question was tongue in cheek. Even if not, IMHO the important point is that items naturally want to be filed under multiple classifications. This is labeling systems like Gmail tags take beginning steps towards supporting - an item can have several tags - whereas folder based systems only allow an item to be in a single place.
Geeko/Tristan: Where would I put it, if it came on paper?
First: We have this wonderful tool, computers, and you want to limit it to only imitating what paper can do? That's like saying that you can only 2 levels of indentation in a list, or that you cannot put a folder inside another folder. The sorts of crappy limitations that I have to put up with in OneNote
Second: I worked with paper based filing systems for things like inventions and patents. I might file an item under one category, and then place a note on a card that gets filed in another category.
Geeko/Tristan: Which of these categories has the most attention?
Today, category 1 (say, inventions related to artificial intelligence and deep learning).
Next year, category 2 (inventions related to high performance supercomputing)
Categories change over time.
---
But... present day tools, AFAIK, make it hard to deal with overlapping and evolving categories.
E.g. Google had to provide a folder like interface for its labels. Copying amounts to adding a label. Moving amounts to deleting old labels and adding a new label.
We have to deal with the tools we have. Today we have folders and search, and primitive tags/labels/categories. Geeko/Tristan's advice applies, if you are using folders. But the search-centric advice also applies, and may save time.