notmuch

Notmuch is an answer to Sup. Sup is a very good email program written by William Morgan (and others) and is the direct inspiration for Notmuch. Notmuch began as an effort to rewrite performance-critical pieces of Sup in C rather than ruby. From there, it grew into a separate project. One significant contribution Notmuch makes compared to Sup is the separation of the indexer/searcher from the user interface.