On Fri, Dec 16, 2022 at 9:05 AM ic <li...@benappy.com> wrote: > 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.
Correct, they use the In-Reply-To and References headers to thread the emails. Subject line change is a heuristic, not for threading the emails but for -breaking- the thread. It's a good heuristic. Unless the sender is doing something asinine, changing the subject line signals their intent to start a new conversation. Regards, Bill Herrin -- For hire. https://bill.herrin.us/resume/
