Spaceback

Spaceback helps you free up storage in your mailbox. It finds large or unwanted email and moves it to Trash (always recoverable, never deleted for good), archives old mail to a file on your own computer, and cleans up duplicate WhatsApp downloads.

The desktop app works on your own computer and talks only to your own mail provider. This website offers a demo mailbox and a WhatsApp cleaner that runs in your browser.