I have this habit for a while now. And I noticed people around me struggle keeping their Email inbox clean. Every time I see someones screen with his inbox on it seems like a pipe of emails just exploded in his inbox and he's to his knees in a mix of read and unread emails. So here is how I do it.
When I see an email that I don't want to see again I just unsubscribe from it. all marketing emails, updates from linkedin, Facebook, twitter. I don't need to be alerted every time someone sends me a message or mentions me. So every time I see an email from a company not a person I search for the "Unsubscribe" link and click it. now this one email is gone from my life hopefully forever.
Gmail had the archive directory forever now. since they introduced it years ago I put all emails that I read there. I don't need to see the same email twice unless I have to reply to it later. So that leaves my inbox with unread emails and emails I have to respond to it later.
I try to respond to emails as soon as I read them. unless it require some research or an action that will take time I leave them there and get back to them when I need to. but as a rule I respond almost at the same time I see the email.
It helped me integrating the email in my Emacs editor with Mu4e package I bind the email screen to
SPC M then
bi to get all emails from all inboxes of all my emails personal and work. read them and archive the ones I don't need to see again. respond and close the screen. it takes couple seconds to do that.
I know there is an email when I see the number in my polybar changes
This number shows my unread emails in all of my inboxes. I don't get notifications just this little number. and If I want to focus on something without my eye hitting the bar like when writing this blog post for example. I put the window in Full-screen mode which hides the bar.
This way I can be in the flow of coding or reading then when I'm checking the time I see there is an email and I can switch to it, read it then close the buffer.
All my emails are offline on my machine synced with offlineimap so when I need to search for an email I don't open Gmail interface. just
SPC M and
s for search, write what I want to search for and I get everything from my disk in my editor, read through them and close the buffer when I'm done.
This means I don't need to categorize emails or any complicated filters. just read, archive, search everything when you need it. simple.