thread-based email index, search and tagging (Mutt interface)

 notmuch-mutt provides integration among the Mutt mail user agent and
 the Notmuch mail indexer.
 .
 notmuch-mutt offer two main integration features. The first one is
 the ability of stating a search query interactively and then jump to
 a fresh Maildir containing its search results only. The second one is
 the ability to reconstruct threads on the fly starting from the
 current highlighted mail.