Question: Mail app not displaying some messages
I am currently using an iPhone SE with iOS 10.3.3. Sometimes, appartently randomly, the Apple Mail app does not show some emails in the inbox. They can be retrieved if I use the search bar (for example, for the sender or the subject) - but of course I don't usually know I have a missing email, so that's a great issue to me, as I end up missing the email completely. The emails display fine on my desktop (on Outlook) and online. This happened to any account I have logged on Mail (gmail, hotmail, one work and one university account), apparently randomly and - I hope! - not so often. All the accounts are set to unlimited (or very high) temporal length, and the emails are just in the middle of others, so I don't think it's a temporal issue.
Please, any hint/though appreciated, thanks!