Change priority of an incoming message
You can change the priority of incoming messages with a script.
Open Script Editor and paste the following in it.
do shell script "sqlite3 ~/Library/Mail/V5/MailData/'Envelope Index' 'update messages set flags = flags | 196608 where flags & 196608 != 196608;'"
Save the script with the name mail_reset_msg_priority2normal in your user path as follows:
UserName/Library/Application Script/com.apple.mail/mail_reset_msg_priority2normal
Note you may have to turn on hidden folder visibility to do this.
You may also have to change the path from "V5" to something else depending on the mail version you are using. Use the largest "V" number in the Library/Mail folder. There could be more than one if you upgraded.
Quit ScriptEditor.
Then in Mail open preferences/rules. Create a new rule that includes at least the following condition "priority is high" and perform
Run AppleScript (using file) mail_reset_msg_priority2normal
Works great. I can't remember where I say this, but when I searched for it I couldn't find it. This solution is not original to me.
Cheers.