FYI - the prob I was having getting Mail to work turned out to be some unknown corruption deep in the bowels of the OS that was magically cured by a simple, quick procedure known to the cognoscenti as an Archive and Install which is rather like an old-fashioned Clean Install With A Twist.
So, one Complete Install of Jaguar and 10.2.8 Combo Updater later, Mail began working like a charm!
ALL of my cosmetic and convenience personalizations WERE preserved, and a handful o' applications required reinstallation to regain full functionality, but for my First One, it went quite smoothly and was fairly 'painless' on the whole.
NB: while it was not complicated, it was not in fact quick (I was being sarcastic above), and should you be contemplating this procedure on your system, I estimate that the main procedure took about two hours (I did not have the forethought to note when I began and when I concluded) with maybe another hour spread out over the next few days as I discovered things that needed some mo' fixin' and attended to them - and this was on my 'fast' machine, the G4 dual 800.
So I have been using Mail for a week or so, and while it lacks a few conveniences, I am overall fairly comfortable and satisfied with it.
- kbeartx