Cannot log out of Gmail

Question

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?

Answer 1

I believe I've worked around the problem:

Settings > Storage -> Other Apps -> Gmail

Click "Clear Cache" and "Clear Data".

The storage usage amount reassuringly decreased, and the app no longer shows my emails.

As a precaution, I did this for every other stock app on the phone also, some of which also appeared to have a large amount of saved "user data", despite the phone only ever being purchased and used for 1 banking app.

As an additional paranoid step, I then created and logged into a blank throwaway account, logged out of it and deleted all the data again.

Answer 2

Boann's answer should help, but I prefer to even disable the application. When you uninstall GMail application updates (that can be found in the same screen from which you uninstall it, on some Android versions as a button, on other in a menu), you can disable the application (the button should appear where the uninstall button is for uninstallable apps). Unless you enable the application again, there will be no GMail application available for use on your device.

Beware of that the Play Store can enable applications. I recommend disabling Play store app too, unless you are going to use it in near future.