How to establish rules on Mail app?
how are emails selected to go into my "important" mailbox?
Can I change those rules?
Does mail I delete from my inbox that is also in important also get deleted?
[Re-Titled by Moderator]
iMac 24″, macOS 13.4
You can establish rules as allowed by the selections in the panels. Not knowing how your rules are set up makes the question hard to address.
Mail doesn't delete unless you tell it to or have a rule that forces that.
Open Mail. Mail in menu > Settings > Rules