It’s not only impossible to respond to every query, it’s perfectly okay to not respond to everything, particularly when lack of response is due to lack of interest. – MINIMALIST PARENTING, Chapter 5
Minimalist Parenting camp described a three-touch rule for email. The first pass is for deleting messages that aren't addressed to you and responding to time-sensitive matters. The second pass is for emails that require more time. The third pass is for the messages that bug or don't interest you. If you haven't responded yet after seeing it three times, you won't! Get rid of it.