The Chrome PushManager only gives an opaque end-point for each of the subscriber i.e a key like ‘APAg1bHPffi8zclblBDcToXN_LEpT6iA87pgR’. We do not have the ability to directly map this to an email of a user.

However, if have the ability to determine the email or any other of your internal mapping of the user at the time of subscription, we provide you the ability to store that information along with the key.