"However, given the number of my correspondents, it would be self-defeating organize the mail that way. The sheer volume would entail a series of nested folders. Once you get to that level, you're applying organization for organization's sake--never a very efficient means of operation."

The term I used was "regular correspondents"; it'd obviously be bonkers to have a folder for each and every person who e-mailed you. That done, you could have a folder for, say, "miscellaneous artists" or "new projects" or "bills" or . . . into which you could sling whole categories of correspondents. (As example, I tend to have a separate folder for each publisher I work with to any substantial degree; I may or may not give individual staffers subfolders within those folders.)