mail-rulesmail.app
As I understand it, active Apple Mail rules automatically get applied when mail comes into the Inbox.
Is there a way to prevent rules from being applied automatically, so that they are only applied when I click the "Apply Rules" menu item (or use the shortcut, cmd-option-L)?
To add a rule in Mail, open Mail preferences (Mail > Preferences… or ⌘+,) and go to the Rules pane.
The Apply Rules function applies to all rules whose "Active" checkbox is ticked.
Try deleting the rule and creating a new one. Mail seems to randomly corrupt things on even the most well-maintained machines, the past few OS iterations. Passwords disappear. Then there is the step of trashing your Mail preferences, as preference files do get corrupt.
Best Answer
Apple Mail rules run automatically only the first time they're set. After that rules will only run manually.
Going into Preferences and unchecking 'Active' will deactivate the rule and will never run it.