On an Android phone I had to log in to my Gmail account to update an app via the "Play Store".
I noticed (to my extreme annoyance) all my emails appearing as notifications on the phone's front screen.
Once I was done, I logged out of the account, via Settings > Users & accounts > Remove account.
The notifications of my emails did not disappear, but I then cleared them manually. As a precaution, I checked the Gmail app, and it appears to have downloaded a total copy of my entire email history into some kind of cache.
On my computer, I removed forcibly signed the phone out, but this had no effect.
The Google help page "Sign out of Gmail" says:
The only way to sign out of the Gmail app is to remove your entire account from your phone or tablet.
That is what I did.
I assumed there must be a glitch. I guess Google never tested this properly, because, they figure, who would want to log out from us?
So I logged into the account again. This time, to sign out, I went via the Gmail app itself.
This successfully cleared it, and when I went back into the Gmail app, it showed no emails and asked me to set up an account. Thank goodness.
Still paranoid, I switched the phone off and on again. The Gmail app now shows everything again. The phone is not logged in, it is disconnected from wi-fi, checking on a computer shows the phone has been signed out.
The Gmail app shows every message I ever sent or received, without any password. This is a shared phone. It gives no option to sign out, because the accounts page says I have no account signed in.
What do I do?