Email verification

Catch-All Domain Detector

Detect whether a domain is catch-all (accepts every address) by probing its mail server over SMTP with a random address. Free — no email is delivered.

Detect a catch-all domain

Enter a domain. We probe its mail server with a random address to see if it accepts everything (SMTP, port 25).

Port 25 must be reachable from the server running this check. No email is delivered.

What this catch-all detector does

Probes the domain with a random address
Detects accept-all (catch-all) configuration
Runs a real SMTP RCPT TO check
Never delivers an actual email
Shows the server's SMTP reply code
Explains what catch-all means for verification

Common use cases

  1. 1Knowing if mailbox checks will be reliable
  2. 2Understanding why verification is inconclusive
  3. 3Assessing a domain before verifying its addresses
  4. 4Auditing your own domain's configuration
  5. 5Interpreting "risky/unknown" verification results
  6. 6Deciding how much to trust a verified list

Related tools

Mailbox Existence CheckerDomain Email ValidatorEmail Address ValidatorBulk Email VerifierMX Record LookupSMTP Server Tester

About catch-all domains

A catch-all (or accept-all) domain is configured to accept mail for every address at the domain, whether or not the mailbox exists, then sort or discard it internally. Many businesses run catch-all so nothing addressed to them is lost.

The catch is that catch-all makes per-mailbox verification impossible: since the server accepts a random, made-up address, it will also "accept" any address you test, so you cannot tell real mailboxes from fake ones. This detector probes with a random address — if the server accepts it, the domain is catch-all and any mailbox result there is unconfirmable. Port 25 must be reachable, and no mail is delivered.

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FREQUENTLY ASKED QUESTIONS

Got Questions? We Have Answers.

What is a catch-all domain?

A domain configured to accept mail for every possible address, whether or not the mailbox exists, then sort or discard it internally.

Why does catch-all matter for verification?

Because the server accepts any address, per-mailbox verification becomes impossible — you cannot tell real inboxes from fake ones on that domain.

How does the detector work?

It connects to the domain's mail server and issues RCPT TO for a random, non-existent address. If the server accepts it, the domain is catch-all.

Does it deliver an email?

No. The transaction stops after the RCPT TO response. Note that port 25 must be reachable from the server running the check.