> On Dec 16, 2022, at 12:04 PM, ic <li...@benappy.com> wrote: > > Hi there, > >> On 16 Dec 2022, at 17:13, William Herrin <b...@herrin.us >> <mailto:b...@herrin.us>> wrote: >> >> Most email clients assume that a change to the subject line (other >> than adding "Re:" to the front) indicates that the sender wants to >> discuss a new topic related to but meaningly different from the last. > > Although I generally agree that changing the Subject line without reason is > an annoyance, I didn’t notice any issue with it until I came across this > thread, which wasn’t broken in my mail client (Apple’s Mail.app).
As a user of Mail.app as well, it is not broken for me either. However, reason being — Mail does not use just the subject to thread. I used to nerd out about email (top + bottom posting, etc) so the details of how Apple Mail threads have been lost in my ADHD riddled brain, but — that’s why. > > This led me to a few tests, and FWIW even Mutt seems happy with the Subject > changing and still threads the emails appropriately. > > In my experience, threading is done by clients looking for the In-Reply-To: > header, not subject. Subject is a heuristic fallback, in case In-Reply-To is > absent. > > Some email clients (although I don’t remember which ones) remove In-Reply-To: > when the Subject: is changed (that might go as far back as my Gnus Oort days). > …. and now that I wrote the above email response, I think you’re right. In-Reply-To: I believe, is how Mail.app does it. (And several others)
