Bulk catch-all checker: find which domains accept every email address
A bulk catch-all checker tests many domains at once to see whether their mail servers accept every address. For each domain it asks the mail server, over SMTP, about one random address that can't exist: accepted means catch-all, rejected means addresses there can be verified one by one. 25 domains an hour without an account, 200 signed in.
Sample result
acme.example is catch-all: its server accepted an address that can't exist. globex.example is not.
- Domain
- acme.example
- Probe
- Random address accepted
- MX
- mx1.acme.example
What this means for you
Addresses at catch-all domains can't be confirmed one by one, so treat them as risky.
- Catch-all, not catch-all or unknown per domain
- One random address per domain, never a real one
- 25 domains an hour, 200 when signed in
- Answers kept a day; CSV download
- Catch-all
- SMTP
- Bulk
By SimpleVerifier Team · Last updated
How do I check a list of domains for catch-all?
- Paste up to 25 domains, one per line (200 when signed in with Google), or email addresses; only the domain of each is used. You can also upload a CSV.
- Press Check catch-all. Each domain's MX records are looked up, then its mail server is asked about one random address we generate, five domains at a time.
- Read each row: catch-all, not catch-all or unknown, with what the server did. Filter by result.
- Download the CSV, then verify the addresses on the domains that aren't catch-all.
Example
- You enter
- Two entries pasted one per line:
acme.exampleandsales@globex.example. - You get
acme.examplecomes back Catch-all: its mail server accepted a random address that can't exist.globex.examplecomes back Not catch-all, because its server rejected the random address, so each address there can be verified. Rows also show the MX host and whether the answer came from the day's cache.- Limits
- Up to 25 domains an hour without an account and 200 an hour when signed in with Google. Runs stop early, with a message, when the day's mailbox-check allowance for free tools runs low; it resets at 00:00 UTC.
How do I check if a domain is catch-all?
Ask its mail server about an address that can't exist. The checker connects from our verification server, says RCPT TO for a random address such as sv-catchall-probe-3f9a…@domain, and hangs up before any message is sent. A 250 answer means the server accepts mail for any address: a catch-all, or accept-all, domain. A 550 means it checks mailboxes, so real and made-up addresses can be told apart.
The probe address is generated by us and never one you type, so the tool can't be used to test whether a particular person's mailbox exists. The domains you paste are the only input.
Why are some domains unknown?
Some mail servers never give a straight answer to a probe. Greylisting defers the first attempt with a temporary error; some servers block verification probes or drop the connection; consumer providers such as Gmail and Outlook.com hide mailbox status, so we don't probe them at all. Domains without an MX record, or that don't exist, are unknown too. Each row says which applies.
Why is the limit lower than the other bulk tools?
Because each domain costs a real SMTP connection from our server, and mail servers and hosting providers limit how many a server may open in a day. The DNS-only tools can check 100 domains a minute; this one checks 25 domains an hour without an account and 200 an hour signed in, and answers are kept for a day so a repeated domain isn't probed twice.
Paying customers' lists share the same daily allowance, so this free tool stops early when the day's remaining allowance runs low and says so, rather than queueing your list or guessing. The allowance resets at 00:00 UTC.
What should I do with catch-all domains?
Treat their addresses as risky rather than valid: the server will accept the message whether or not the person exists, and may bounce it later. Our post on sending to catch-all addresses covers when it's worth it. For the domains that aren't catch-all, verify each address before you send, because there a mailbox check gives a definite answer.
How is this different from the single catch-all checker?
| This bulk checker | The single catch-all checker | |
|---|---|---|
| Domains per run | 25 an hour, or 200 signed in | One, five checks a minute |
| Input | A pasted list or CSV of domains or addresses | One domain or address |
| Output | One row per domain, filters and a CSV | One detailed verdict |
| Probe | One random address per domain | The same |
Who uses this tool, and for what?
- Cold emailers
- Find which prospect domains are catch-all before you decide how much of the list to send to.
- Sales ops
- Tag accounts whose addresses can't be verified, so reps know which bounces to expect.
- List cleaners
- Split a B2B list into domains where verification is definite and domains where it can't be.
- Deliverability consultants
- Explain a client's high accept-all rate with the domains behind it.
What can’t this tool tell you?
- Each domain is probed once. Greylisting, probe blocking and providers that hide mailbox status give unknown.
- A server can accept at RCPT TO and still bounce later, so not catch-all is about the server's answer, not every address.
- 25 domains an hour without an account, 200 signed in; runs stop early when the day's mailbox-check allowance runs low.
- Results are kept for a day per domain, so a change made today can show tomorrow.
Common questions
- How do I check if many domains are catch-all?
- Paste them into a bulk catch-all checker like this one. It probes each domain's mail server with one random address and reports catch-all, not catch-all or unknown.
- Is the bulk catch-all checker free?
- Yes. It's a free tool: 25 domains an hour without an account and 200 an hour when signed in with Google, with no card.
- Does it send an email?
- No. It starts an SMTP conversation, names one random recipient and disconnects before any message is sent.
- What does catch-all mean for my list?
- Addresses at a catch-all domain can't be confirmed by a mailbox check, because the server accepts every address. A verifier marks them risky or accept-all; you decide whether to send.
- Why does Gmail show as unknown?
- Gmail and other consumer providers don't reveal whether a mailbox exists at RCPT TO, so we don't probe them. Their behaviour is the same for every address on the domain.
- Why did my run stop early?
- Either you reached the hourly limit (sign in for 200 an hour), or the day's mailbox-check allowance on our server ran low. The message says which; the daily allowance resets at 00:00 UTC.
Sources
Every address left in your cleaned list still need a mailbox check.
This tool removed what can be found without contacting a mail server. Whether each remaining mailbox actually exists can only be answered by asking the server that hosts it — an SMTP check — and that is what the paid plan does.
- Upload the cleaned file as it is — CSVs up to 100,000 rows
- A real SMTP mailbox check on every row, with catch-all detection
- Valid, risky and invalid exported as separate files
One plan, cancel anytime, no contract. Sign in with Google and your first 100 email checks are free, no card. The free tools stay free either way.