I know I am just preaching to the choir here but it is quite jarring how bad the mail app is at this stage of iOS 13. When the first beta launched in June, I was thinking, "ok - I get it, super early, super raw but it will be polished by September". It is now mid-November and it is maybe 50% of the mail bugs have been fixed.
For my own relatable experience, I sent an important email last Thursday, hit the send button and was on my merry way. Found out that despite my perfect signal, it never actually sent. It mysteriously vanished and as a consequence, I had a poor showing at a company meeting.
Have people just jumped to Outlook for iOS? Last time I used it, it felt disconnected from the rest of iOS since it cannot be treated as native but maybe it is worth the trade-off.
This exact same thing happened to me today, on iOS 13.3. None of the emails I sent out today actually made it to anyone. I couldn't believe it when I got home and none of the emails I sent out were in my sent folder. I was wondering why I didn't hear back from certain people and now I know why, they never got any communication from me. Absotutely unacceptable and Apple is an embarrassment for having a stock app this bad this deep into the OS. Shockingly awful is the only way I can describe it.