Adding Sandbox Tester in iTunes Connect with an existing Apple account

Question

I\'m trying to add sandbox testers in iTunes Connect. But I\'m getting this error:

The email address you entered already belongs to an existing Apple acco

Answer 1

For each sandbox tester, you’ll need to collect the following information:

Email address that has never been used as an Apple ID to purchase iTunes or App Store content, nor associated with any existing Apple ID. Consider creating a dedicated email address for each sandbox tester.

https://help.apple.com/app-store-connect/#/dev8b997bee1

This means that you cannot use use an existing Apple ID or @icloud.com email as a sandbox tester.