A proportion, or a large proportion, of the e-mails in your in-box are probably digital newsletters, or updates for organisations or products for which you registered long ago.
And probably you receive for too many of these, so that you can no longer get a clear overview of your in-box. There is now a web application from Swedish developers that can help you quickly and easily: Deseat.me. You can log in with your Google or Outlook account.
You get a handy overview of all the services for which you have ever registered, and you can select for each registration whether you want to retain it or cancel it. With a few clicks, you can tidy everything up!