Why does the Lumia 640xl remove emails from a webmail server?

[Windows Central Question]

why does the lumia 640xl remove emails from a webmail server?

I upgraded from a lumia 920 to a 640xl and now it removes all my emails from my email accounts webmail server even though I have not deleted them. I can be reading an email then all of a sudden the email disappears. This did not happen with my 920 and my home computer is set to leave all emails on the server.