I have multiple email aliases that feed into the same box. I filter messages based on what alias they went through and who sent them. Nearly all messages get automatically marked as read; they're there, but I won't get notifed of them. For a few high priority senders who have my high priority alias, they get the star treatment: notification, star, reminder to reply, etc.

Also, if you filter for the word "unsubscribe," you can cut through a good chunk of low-priority automatic messages.

I am familiar with vendors that provide a similar service, but none quite as you described. Which one do you use?

It's just Google. I have a Google Workspace subscription for my personal domain, but you can accomplish a similar thing using "plus-aliases" on standard free Gmail accounts: "foobar+lowpriority@gmail.com"

Get good at searching, filters, modifiers, keywords, etc. My I boxes are huge, but I generally find what I need quickly by typing a fee searching filters and keywords

It is a good replacement for letters, postcards really. It does that well, and that’s enough.