Apple Mail is hiding certain messages without any identifiable reason

Apple Mail on m MacBook Pro, iPhone and iPad (all running the latest software as of Sept 6 20222) is hiding certain messages from me. I have no active Apple Mail rules. The way the messages are hidden is totally bizarre.

Background: My company has a typical commodity web hosting and IMAP e-mail provider that provides email for my company's domain. The hosting provider claims no knowledge of this problem and has no explanation for it. My company has a contact form on the website that sends mail from contact@domain.com to contact@domain.com. Contact@domain.com is a mailing list that includes me and a few other people.

I receive all e-mail sent directly by anyone directly to contact@domain.com normally. When someone fills out the contact form and the data is sent from contact@domain.com to contact@domain.com everyone except me receives the email . The email is not found in spam or trash. I have no active mail rules that would cover this (or anything else, there are no rules). The same behavior occurs on my iPhone and my iPad. This contact form used to work for me also. This problem appeared out of nowhere a few months ago and has remained consistent for 3-4 months across multiple macOS and iOS software updates.

We have not been able to find any reason for this. I am the only Apple user on the mailing list.

What I just discovered recently is that if I login to the hosting providers webmail, these emails show up as unread. It's as if the Apple Mail client on all three of my devices simply ignores the existence of these messages when syncing to the server.

contact@domain.com is also not blocked, but even if it was the behavior selected is to move it to trash but these messages are not found in trash, while messages from all other addresses that I have blocked do appear in trash.

How could I resolve this issue? It must be something specific to Apple because nobody else in my company has this issue.