is there a way to unsubscribe from 600+ subscriptions?

John, I could help you with that. It would require taking the site down a bit to pull backup, make manual database updates, and get it going again. I could loop this in next time we need to do that for some other reason.

Any specific threads you're getting a ton of emails on? You'd might be better of unsubscribing to those individually- since most older subscriptions aren't active.