Catch-all email domain test
Enter a domain to find out whether its mail server accepts email for any address (catch-all), which means individual mailboxes on it cannot be confirmed.
Free: 5 checks every 2 hours. No email is sent.
How it works
The tool makes up an address on the domain that almost certainly does not exist, such as eev-test-8f3k2q@example.com, and asks the domain's mail server whether it would accept mail for it. No email is sent.
If the server accepts that address, it accepts everything: the domain is catch-all. If it rejects it, the server checks its mailboxes, and addresses on the domain can be verified one by one.
FAQ
What should I do with catch-all addresses?
Keep them in a separate segment instead of deleting them: many are real. Send to that segment in smaller batches and watch the bounce rate.
Why would a domain be catch-all?
Some companies want to receive mail sent to misspelled addresses, and some security gateways accept everything first and filter later.
Why can the result be "could not confirm"?
Some mail servers answer slowly, ask to try again later (greylisting) or block checks. Try again in a few hours.