When you say that you deleted the folders from your email account, were you using a dedicated email client (such as the Windows 10 Mail app or Thunderbird) or accessing your account via your email provider's website?
If it was the former, try using web access instead. Then you'll be able to delete the folders directly on your provider's server, rather than locally on your laptop. (If the folders no longer exist on your provider's server though, delete your account from the Windows 10 Mail app, or whatever, and recreate your account. Then everything that's still on the host server will be downloaded to the app).