To their credit, Apple Support on Twitter played 50 questions with us. They wanted to determine whether it was the IOS or software added. We left it when they asked us to do the following and made no reference to any push issue from mail ISP, you would think they would know:
1. ) restore phone to out a "new" out of box state, then setup and check mail.
2.) if that worked, they would work with us to do a limit restore of info in our backup.
3.) If it still did it with the "new" state restored, they would get with engineers.
We/my wife opted to download Edison, all works normal using the Edison Application.
BTW, my wifes phone was a wiped 7 plus that was restored with her 6s plus backup, which worked fine, but also had not been updated. We then gave that phone to my daughter, she accidently updated it and guess what, you got it.
Also, my old blackberry Q10, same mail ISP, does not do this. (No it's a pre android)
Download the application called Edison.