First, what is the email provider? GoDaddy, by any chance?
Second, in the case like you described, does opening the app and using the account's refresh button get the "missing" message?
Thank you for you interest. The problem turned out to be the phone itself, and I caused it. I used some third party "optimzer" that affected several apps. I tried deleting and reinstalling AquaMail, but that did not solve the problem.
I had to go through the big effort or resetting the phone, and then reinstalling all of my apps (luckily I had a list of them). Syncing my contacts, etc., was quite easy.
After I reinstalled AquaMail I was at first experiencing a problem with the phone (Knox Manager) blocking incoming emails if wi-fi was off. With wi-fi on, all email came through. After a number of hours, Knox Manager stopped blocking calls with wi-fi off, and AquaMail is running perfectly.
You have created a wonderful product, BTW!
EB