iPad missing Emails in the Folders- open and nil is there in any folder- all gone

Unless you are using a POP3 mailbox, the vast majority of modern email systems keep all of your mail on the Mail Provider's mail server - with a local copy being downloaded to the client device(s) such as your iPad, iPhone, Mac or other computer - all being synchronised via the mail server.

Before doing anything else, you would be best advised to verify that your mail messages are still present on your Mail Provider's server. Simply sign-in to your Mail Providers webmail service using a web browser. When you are confident that your mail messages are still present on the server, you can proceed to resolve the problem with your iPad.

Deleting and re-adding your email account is often the easiest way to resolve a problem with a specific Mail account. After deleting the account, perform a forced restart before re-adding the email account to your iPad.

• Delete account:

Settings > Mail > Accounts > [Your Mail Account] > Delete Account

• Force restart the iPad:

Force restart iPad - Apple Support

• Add Mail Account:

Settings > Mail > Add Account