202212160543.AYC Re: eMail Conventions

Fri Dec 16 17:04:23 UTC 2022

Hi there,

> On 16 Dec 2022, at 17:13, William Herrin <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).

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).

BR, ic.

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