Reducing Mail box size without losing specific senders

From time to time I have managed to get rid of a few scores or hundreds of no longer or never wanted mailings by searching for a particular sender and then deleting, but as I have over 200,000 emails this is too slow and labour-intensive.

I have to confess that I have never become familiar/competent with how Mail works in Mac, and so the Inbox and its subsidiaries get bigger and bigger all the time, and have been doing so for years (since well before I began using Apple computers).

If there were a way of doing it, what I'd like to do would be to nominate some senders to protect and then – if possible with some safety measures in place – delete everything else. I suppose it would be ideal if I could begin by going back to emails fifteen years + old, tell the system the names of all protected senders, and then be presented with a list of all the emails that arrived UP to then, excluding the protected ones, so that I could check that nothing important was at risk and protect them, and then delete all that were left. And then repeat the procedure a year at a time.

If I could clear the decks like this I might feel pushed into getting to grips with whatever machinery Apple has to prevent this sort of chaos for the future.

(I much prefer Apple to PC computing in most ways, but I have to say that I found the Windows Rules for sorting emails easier to implement than the Mac equivalent.)

Is what I want to do totally out of the question?

[Re-Titled by Moderator]

Original Title: Is there a way I could drastically reduce the HUGE size of my MacMail boxes without losing a few named senders?