My issue is that some email messages I delete from my PC don't sync with the mail app (i.e., the email messages remains on my iPad or iPhone). When I try to delete the mail from my iOS device, the app tells me that the message couldn't be deleted from the server and unfortunately the mail message remains in my inbox. To fix this, I turn off my mail account in settings and then turn it on again and the mail re-syncs. This happened every once in a while to me in iOS9 (maybe once per month), but it is happening daily on two devices that I have that are running the beta. Note that this does not happen for the same messages on both devices, which is very strange. I have not read that anyone is else experiencing this, which is strange. anyone?