Merging mail backup with current

OK. I now have completed my "correct" upgrade to KDE 2.2.1. I will work on
a document of what I had to do. This dependency thing in Linux is something
a non-geek would never, ever want to touch. It is something that must be
address for Linux to move from geekdom to everyone else.

Anyway, now I have a backup of literally years of emails and I have this
current set of email files from the last week or so. How do I merge the two?

I am using Kmail 1.3.1. Lots of mail folders.

Alan