There's no way you're ever going to get to all of those old emails. It's useless. Plus the more you answer, the more you get back. Give up — or at least retreat.
Currently I have (or had) 756 emails in my inbox. If I break it down, at least 25% is garbage, another 50% relevant a few weeks ago but not now. The rest may or may not be important. The important ones usually have a chat thread with them or they have been sent more than once.
So the vast majority of my emails, and probably yours, are useless baggage.
Here's what I did today: I dedicated exactly 30 minutes to complete this task. Working back from today's emails, I reviewed and handled as many as I could. Once I hit 30 minutes, I deleted everything below. Boom. In one click I felt renewed. It might cause some anxiety, especially if you are as meticulous as I am. But I promise, if anything in that bunch was important, someone will let you know.
I can't speak for you, but I will never be able to master my email inbox. I have accepted that fact as I accept gravity. And we have a saying in neurosurgery: Gravity is undefeated. But after this inbox cleaning, it's easier to be more decisive about new emails and required actions. Try it, you might like it.