On Fri, Jan 15 2016, Daniel Kahn Gillmor wrote: > So where is the case-insensitive lookup happening? Is this a bug in > mml-mode, or in notmuch-emacs? It's caused by behaviour in mml2015.el (hence upstream). `mml2015-epg-check-user-id' uses `equal' to compare the recipient from the composition buffer with the addresses from the matching key. The simplest way to get the desired behaviour would be to `downcase' both strings before comparing.