I think Mailing List Mode is full out no muting or notification settings working. You might instead want to set the categories you care about to Watching, which will set each new topic in those categories to Watching, which should generate emails for all of them like you want.
It should also mean you can unwatch topics, even in categories you’re watching, or watch select topics in categories you’re not watching.
To set the notification status for a category, go to that category, and hit the circle in the top right.