Hi Gio,
Thanks for this feature request! It's always gratifying to know that someone is using mumi, especially its more advanced features! :-) > IMO is useful to be able to search for "subject:foo", it's a different > search than searching for foo in the body It looks like we implement this already. See https://git.savannah.gnu.org/cgit/guix/mumi.git/tree/mumi/xapian.scm#n141 A search for "subject:foo" should work already. Cheers! Arun