The tools you will run into most often are ZeroBounce, NeverBounce, BriteVerify, DeBounce and MillionVerifier.
They all work the same way underneath: an SMTP handshake with the receiving mail server to ask whether an address exists. That is genuinely good at sorting clearly valid addresses from clearly invalid ones, and it is fast.
Where they stop is catch-all domains. Those servers are configured to accept every handshake, so the question comes back answered the same way for a real mailbox and a made-up one. The tool has nothing left to go on and returns *Catch-All*, *Accept-All* or *Unknown*.
Scrubby is built for exactly that leftover segment — it is a complement to these tools, not a replacement. Keep using the one you have, and send it what it could not resolve.