I filter all messages with the word "unsubscribe" in the body into a "Bulk Mail" folder that I check once a week, works beautifully. As for the per-category ad

I filter all messages with the word "unsubscribe" in the body into a "Bulk Mail" folder that I check once a week, works beautifully. As for the per-category addressing, you can add "+flights" to your username when subscribing to flight notifications and then filter on that however you like...