202212160543.AYC Re: eMail Conventions

Joel Esler joel.esler at me.com
Fri Dec 16 17:21:10 UTC 2022

> On Dec 16, 2022, at 12:04 PM, ic <lists at benappy.com> wrote:
> Hi there,
>> On 16 Dec 2022, at 17:13, William Herrin <bill at herrin.us <mailto:bill at 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)
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