I kept getting notifications asking for my Hotmail password which I thought were a scam, they were coming through every 15 minutes all day and night but it didn't say from who and it did not appear to be any of my apps which did not have permissions anyway.

It looked like the Hotmail log in but no way was I going to put in my password, in any case I had deleted the Hotmail app as there was not enough memory space remaining after Android bloated itself and installed all sorts of other rubbish which I have to constantly remove.

Then I noticed that some circle symbol on the supposedly Hotmail log in used the Google colours, it turned out to be G-mail sending me the notifications without saying so or why, like you I used the G-mail app to read Hotmail, I had given my password & could not work out how they could have lost it (your upgrade suggestion sounds probable) or why they would not say so and ask for it again instead of sending a Scam sounding warning message every 15 minutes with the as it now turns out to be the real Hotmail log in page.

Long answer but after deciding it was legit I gave my password, it was that or smash the phone with a hammer as the notification tones were driving me mad, & Hotmail is now synced once again.