Notmuchmail helps to do fast, global-search and tag-based email system to use within your text editor or in a terminal. "Not much mail" is what Notmuch thinks about your email collection. Even if you receive 12000 messages per month or have on the order of millions of messages that you've been saving for decades. Regardless, Notmuch will be able to quickly search all of it. It's just plain not much mail.