The "valid" email that isn't: catch-all domains and the metric they quietly break
Something that tripped us up early: a lot of email validators mark catch-all domains as "valid" — because technically the domain accepts any address. But that doesn't mean the specific mailbox exists. So your bounce rate looks clean in testing and then climbs once you actually send.
It's an easy trap for anyone doing list building, cold outreach, or even just cleaning a signup list — the failure doesn't show up until you've already spent the send.
We ended up building catch-all-specific detection into our own API for exactly this reason, mostly because it kept biting us with our own lists before we did anything about it.
Curious if others have run into this — how are you catching it, or are you just eating the bounce rate as a cost of doing business?
Email validation looks simple until you deal with edge cases like catch-all domains, disposable emails, and risky addresses.
Interesting how the right choice depends more on the workflow behind the validation than just accuracy claims.