For me it’s three. In addition to my main inbox, which serves as a holding pen for my most pressing matters (i.e. messages that I must respond to before I go to bed), I make use of only three email folders as follows:
- “Action this week” folder: Everything that requires a response before the end of the week. (I will respond to these on Friday afternoon; my way of getting revenge on the person or organization who sent me the original email in the first place.)
- “Happiness” folder: Emails that brighten my day or make me happy in some way (e.g. a thank you note from a student, an acceptance of publication from a journal, or other good news) go here.
- “Zafacón” folder: I dump most of my emails into this massive catch-all folder (out-of-sight, out-of-mind!), just in case I may need to reference a particular email again, or if I am otherwise unwilling to hit the “delete” button. (In Puerto Rico, the word “zafacón” is slang for a general or all-purpose category.)