Mark Walters <markwalters1009@gmail.com> writes: > By default the reference header is hidden. It is controlled by > message-hidden-headers which you can customize. (Note notmuch adds > user-agent to this list via notmuch-mua-hidden-header.) Thanks for explaining this! So I posted about one problem, and instead got a solution to a problem I didn't even realize I had. Adding: (setq message-hidden-headers (delete "^References:" message-hidden-headers)) to my eval-after-loaded notmuch-config.el file solved this problem cold. No more unintentional References: headers for me. Arguably, I would say either both the In-Reply-To and the References header should be hidden or neither. Otherwise, what was happening is that I was deleting the In-Reply-To header as it was the only one I saw, and figuring that maybe References was adjusted after the fact based on In-Reply-To. After all, the message buffer doesn't keep track of the parent message. Unless there's a reason that someone would want to alter In-Reply-To without altering References, it doesn't make sense to show one without the other. David