Mail hides some messages but show if you search for

Hello,

This is macOS Sierra on MacBook Pro early 2015) though the problem existed on previous versions of OSX.

I have a serious problem in my Mail. It does not display some messages in any folders (Inbox, Trash, Junk, Archive). Yet when I search for, I find it.

Yesterday, I checked in on line for my flight from Europe back to Australia and chose to email the boarding pass to me. I gave my .me account. Because nothing came, I selected second email account to email the boarding pass to. This time it was my provider's email (Telstra's bigpond account). Nothing happen so again I asked to send to another account, the third one and this time to my .icloud account. Nothing again. It was late I went to bed.

Next morning I found the email only in my Telstra account. I decided to search for the email using the phrase from the Telstra account email. And voila, all three emails were found!

It is hugely disappointing that such important emails can simply be not displayed in the Apple provided accounts! I own iPhone 6 and iPhone 8 and the emails are not shown there either!

As this is random, it is unlikely a setting problem but rather a software bug being there for quite a while (I detected it about 4 years ego for the first time).

Has anybody heard any response from Apple to such a serious problem?

Of course, I now consider seriously abandoning the Apple platform I have been for so long.

Regards,

Chris