Catch-all email checker

What a catch-all domain is

Most mail servers reject an address that has no mailbox behind it. A catch-all domain is configured to accept it anyway, so mail to anything@company.com is taken in and either routed to a shared inbox, held for review, or quietly discarded. Companies set this up so a misspelled name or a former employee’s address does not bounce a customer’s message.

The setting belongs to the domain, not to an address. If one address at a domain is catch-all, every address at that domain is, which is why this tool asks for a domain rather than a person’s email.

How this checker tests a domain

We look up the domain’s MX records, then our verification server opens an SMTP connection to the mail host, introduces itself, and names a recipient with RCPT TO. That recipient is a long random string generated on our side for each check — you cannot choose it, so the tool cannot be used to test whether a particular person’s mailbox exists. The connection closes before any message is transmitted.

A 250 response to an address that cannot exist means the server accepts everything: catch-all. A 550 means it checks recipients: not catch-all. Anything else — a temporary 4xx deferral, a timeout, a refused connection, no MX record — is reported as unknown rather than guessed.

Why verifiers return risky or accept-all

An email verifier asks the same question for the address on your list: does this mailbox exist? On an ordinary domain the server answers truthfully. On a catch-all domain it says yes to every address, so the answer for jane@ is the same as the answer for an invented one. A verifier that reports that as valid is passing the server’s indifference off as confirmation.

Honest tools put these addresses in their own bucket instead — risky, accept-all or catch-all depending on the vendor. Some also have an unknown bucket for servers that would not answer at all, which is a different situation: accept-all and unknown results mean different things and deserve different handling.

Why catch-all addresses cannot be fully verified

Verification without sending relies on the server telling you which mailboxes exist. A catch-all server has decided not to tell anyone, and there is no other channel to ask. Pattern guessing, social profiles and past engagement can raise or lower confidence in a given address, but none of them is the mail server confirming the mailbox.

The same limit applies to this tool’s own answer. It is one probe at one moment. Administrators change their settings, and some servers accept every recipient during the SMTP conversation and only bounce the message after it has been delivered to them — so a domain can look normal here and still produce bounces later. A not catch-all result is strong evidence, not a guarantee.

How to handle catch-all addresses

• Segment them. Keep catch-all addresses out of the send that carries your confirmed valid ones, so any bounces land on a list you can measure separately.
• Send in small batches and watch the bounce rate for each batch before sending the next.
• Prefer addresses with independent evidence — a published address, a reply history, or a format the company is known to use.
• Remove hard bounces immediately and do not re-verify them; the bounce is the answer the server would not give earlier.

The full playbook is in how to send to catch-all emails.

Common questions

How do I check if a domain is catch-all?

Ask the domain's mail server to accept an address that cannot possibly exist. This tool generates a random local part, connects to the domain's MX host, and issues RCPT TO for that address without sending a message. If the server answers 250 accepted, it takes mail for any address and the domain is catch-all. If it answers 550 rejected, it distinguishes real mailboxes from invented ones.

What does accept-all mean in email verification?

Accept-all is another name for catch-all: the domain's mail server accepts every address during the SMTP conversation, whether a mailbox exists or not. Verifiers label these results accept-all, catch-all or risky because the server's yes carries no information about the specific address you asked about.

Can a catch-all email address be verified?

Not with certainty. An SMTP check works by asking the server whether a mailbox exists, and a catch-all server says yes to everything. A verifier can confirm the domain is real and receives mail, but whether jane@ reaches a person or a dead end is only revealed by sending to it and watching for a bounce or a reply.

Why does the checker sometimes say unknown?

Because the probe did not get a clear accept or reject. Common causes are greylisting, where the server defers unknown senders with a temporary error; servers that time out or block verification connections; domains with no MX record; and moments when our probe capacity is in use. Unknown means no conclusion, not a hidden catch-all result.

Should I send to addresses at catch-all domains?

Usually yes, carefully. Many catch-all domains belong to real companies, and the address may well be correct. Keep catch-all addresses in their own segment, send to them after your confirmed-valid addresses, use small batches, and remove anything that bounces. Do not mix them into a send that has to stay under a strict bounce threshold.

This tool classifies a domain. To check one address end to end, use the free email checker; for a whole list with catch-all detection on every row, see pricing.