I have so much digital clutter it's unreal :( My first digital job is to sort out my email as I've got some POP accounts and multiple devices and it is a total shambles and adding to the clutter daily.
We may have more emails than we do dollars of net worth. Both are well into 6 figures.
It's a bit of an extended story, but information retained in my email archive very likely saved a child's life - so I am especially loath to dispose of everything wholesale.
I, for one, would be fascinated to hear the story, if you would like to tell it.
I just moved all the old stuff into a folder called 'Archive'. Then I kept my inbox at zero going forward. Anything I have to act on stays in the inbox, once it's dealt with it gets filed.
I personally use a few simple folders, "Shopping and Bills", "Friends and Family", "Community Organisation" I volunteer with. But I believe research shows it will be just as quick to find something by filing everything in one folder once it's dealt with. Archive, Completed, Dealt With, whatever you want to call it.
I don't see a benefit to deleting everything if you have available storage space.
Oh, one other thing I do, I have a folder called 'Vouchers'. Whenever I get an offer (eg 10% of a hotel stay, free burger somewhere I actually go) I put it in that folder. Then when I need a hotel room, am meeting a friend for dinner, or want new socks or whatever, I check that folder first. I just delete stuff over a month old every so often, though I'm sure you could automate that part. It means less stuff I might not use sitting in the inbox, but I don't worry I'm 'throwing away' something useful.