We've moved to our own in-house click and open tracking infrastructure. This is one of those nerdy esoteric details that you probably don't care about, but here's what's changed:
This change requires no action on your part and is completely transparent. The only difference you might notice is that the URLs in redirection links look slightly different (but, again, you probably won't notice it).
(And, as always, this kind of tracking is opt-in. Buttondown does not track your subscribers' activity without your explicit consent.)