Using a few hints you left on your stack overflow profile I think I've deduced what your app is and what is the problem. I won't mention the app name here as you seemed to want to keep the question general.
The problem is the subtle difference between a superceded release and a shadowed release. Your beta APK is partially shadowed. The beta APK is targeted at users on SDK9+, whereas your production APK is targeted at users on SDK16+. This means while most users will get your production APK, users on older devices (SDK 9-15) will get your beta. As a result, your beta is still technically active, and so you getting the email is correct.
So now the question is what can you do to deactivate it? The answer is a bit confusing in the UI, but makes sense once you think about it. You need to
- create a release with NO (0!) APKs in it
- publish that release to the beta track
This tells Play that you deliberately want there to be no active APKs in Beta. These users will still get production APKs, but your old beta APK will no longer be active. We're sorry this got confusing, you were caught by a subtle edge case.
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