I have multiple times in my life made a real effort to limit the amount of e-mail I receive. And I have tried all kinds of different approaches to how to limit it. For example spending hours subscribing for everything in one go. And I have scheduled a slow each day or week to remove one of a few.
The most efficient approach for me is to sit down once a week and remove ten. I just search for “unsubscribe” and remove ten. And then I do the same next week. The reason I think this approach is good is because then you identify those who have sent you emails recently. And you also have the choice of keeping the newsletter you enjoy.
I only mark emails as spam and blacklist them after making a real effort to get rid of them.