Mail's "All inboxes" doesn't list messages from all accounts

I finally realized that I was missing seeing email messsages because I assumed that when Mail was set to “All inboxes”, it was still just showing messages from one of my accounts. That’s not the case on the iPhone. I couldn’t find a way to work around this. I look at the Apple Communities site and others have noticed this, too. Any suggestions?
Floris

Are you filtering to show only unread messages?

No, I’m showing both read and unread messages.

I find on my iPad Mail actually skips over messages when going through “All inboxes”, and I have to go back and manually select them from the main list to read them. No consistent reason why or when this happens.