I purchased a new Late 2018 Mac Mini in Dec 2019. It is running OS 15.1. (I upgraded from my 2009 Mac Pro running OS 12.6.1)
Since then I have noticed several oddities in the Mail app.
1) My preferences are set to MANUALLY check for messages, but message download and appear at random times while the app is open.
2) Messages I want to keep in my Inbox are automatically being moved to the trash. Just today I moved a message I want to keep back to the Inbox from the Trash for like the 10th time. This was one of 12 messages I had to retrieve from the trash that I did not dispose of. I notice the missing messages from time to time when I open Mail at the beginning of the day.
3) My preferences are set to NEVER delete erased message, but they seem to be deleting after 30 days.
Why have preferences if they are not going to be followed? Any answers or help would be greatly appreciated.