Fast system for indexing, searching, and tagging email. Even if you receive 12000 messages per month or have on the order of millions of messages that you"ve been saving for decades, Notmuch will be able to quickly search all of it. Notmuch is not much of an email program. It doesn"t receive messages . It doesn"t send messages . And for what it does do that work is provided by an external library, Xapian. So if Notmuch provides no user interface and Xapian does all the heavy lifting, then what"s left here? Not much.