We gave up on Apple email more than a month ago, installing Outlook to access multiple Exchange accounts.
It worked immediately (thus pinning the bug clearly on a defect from Apple.)
We actually like Outlook on our phone more than we like Apple's email app. It's almost the same (and had almost zero learning curve) but is more polished and has a few additional features that make our work easier.
So, even when Apple fixes this problem, we won't be going back to the Apple app.
It amazes me that Apple, the third largest company in the world (Fortune 1000, 2016), has such bad QA that this bug got out the door. The only other explanation is that they KNEW about the bug and shipped the product anyway, just to make a ship date.
What amazes me even more is that Apple either doesn't know about this thread, or has chosen to stay mute on the issue, hoping it won't gain more attention. That's called treating your customers like dirt. And it's something we expect from Microsoft. However, I guess we were mistaken in thinking Apple didn't have that kind of contempt for their users.