User-Agent: and In-Reply-To:

From: Graham Perrin <>
Date: Sun, 26 Mar 2023 08:59:22 UTC
Not to start a long debate (or rant), I'm curious.

Mark, Peter, please: what do you use to send email?

A recent discussion is split across twelve threads; screenshot attached.

I looked at headers for a handful of the splits. If I'm not mistaken: 
neither a *User-Agent*: field, nor an *In-Reply-To*: field.