Catch-all (accept-all) domains are the quiet killer of email verification accuracy. On a normal domain, an SMTP server rejects mail for a mailbox that does not exist — so if it accepts, the mailbox is probably real. On a catch-all domain, the server accepts mail for every address, existent or not. That single fact breaks the core assumption most verifiers rely on.
Here is how to detect catch-all domains yourself, and how to skip the plumbing when you just want the answer.
The idea in one sentence
Ask the mail server to accept a random address that almost certainly does not exist. If it says yes, the domain is catch-all.
Doing it by hand (Node.js)
