I have a new M4 Mac Studio. I also have an iPhone 16. Both are updated to the most recent versions of OS 27.
However, the Mail app does not sync properly across both devices. Additionally, the Mail app on the Mac has so strange behavior.
I have two mail accounts, an iCloud account and a Gmail account. It is the Gmail account that doesn't sync between the two devices. Also, after I have viewed new Gmail on the Mac, without deleting them, the mail disappears. However, I can see them in the Gmail account in the Mail app on my iPhone.
I'm a long time user of Apple products and have never had these prolems before, but I'm at a loss of how to solve this.