I have been pretty good about keeping my inbox relatively clean. SpamAssassin does an admirable job of keeping junk mail out, and so I mostly receive mail that I want. So, I typically have 30-40 messages in at any time. That makes it possible to keep track of mail that just accumulates during the workday and that I end up truly sorting out and deleting when I get home. So far, the daily average hovers around 80. That means during the day I received 40 messages that I read or plan to read and that I did not delee immediately because I plan to use them for responses to people and the like. Forty (40!) messages that I find useful enough to keep for at least a few hours.