I have noticed that at times when I check my mail on my iPad, that mail messages will disappear. These are not things that I have rules for on my Mac mail (which is always open), but regular messages. I open Mail, see the message at the top of the list, then it is gone. I just had it happen for my cell phone bill. It was there, then gone. I look in Junk Mail, trash, and even search for it in All Mailboxes, but I can’t find it.
This is really frustrating when I see a message that I want to read and it’s suddenly gone. This is before I can look at the body and read it.
Is this some server culling of possible junk mail, or an expected behavior from IMAP? It does not seem to do it with a particular email address, but most of mine are Apple or gmail.