Those are staggering numbers. I got tired of so much spam. Much from entities I know but will not do business with. lots of news sources too. About a year ago, I started unsubscribing from most of them. The flow of crap dropped significantly.
Now I use rules in Outlook to auto-direct less important emails to separate folders. Check through them periodically. But my inbox stays less than 20 emails, sometimes almost no emails.
One trick is to do all my personal purchases and sign-ups using a separate email account. This keeps non-business items from clogging my business email during market hours.
SEC requires we archive all emails for 7 years (I believe). We have a system that automatically keeps evry email that we can go into, but it is not easily visible in Outlook. So we don't have to keep every email in Outlook "just in case". Instead, we can contact Compliance and have them pull anything using their archive system.