Bulk email domain availability checker: which addresses are at unregistered domains?
In short: Paste email addresses and see which sit at a domain with no registry record and no DNS, which can never take mail, with registrar and expiry for the registered ones. Limit: Reads the domain, never the mailbox: a registered domain says nothing about a particular address.
A bulk email domain availability checker reads the domain after the @ in each address and asks its registry whether anyone holds it. Paste up to 100 unique domains a run, or 500 signed in. A domain is shown as unregistered only when the registry has no record and DNS agrees, so those addresses will bounce. It checks the domain, not the mailbox. Download the CSV.
Registered domains can still have dead mailboxes. Check every address.
Price: this tool is free. Checking a whole email list is from $9/mo, and the first 100 checks are free with Google, no card. Check your list free nowSee pricing
Sample result
tom@globex.example is at a domain nobody has registered.
- Address
- tom@globex.example
- Domain
- globex.example
- Registry record
- None
What this means for you
A domain with no registry record and no DNS takes no mail, so this address will bounce.
- Unregistered only when registry and DNS agree
- Registrar and expiry for the rest
- Never guessed when RDAP is missing
- CSV out, nothing emailed
- Unregistered
- RDAP
- CSV
By SimpleVerifier Team · Last updated
Got a list with addresses at domains that may have lapsed?
- Paste it above to find the addresses at domains nobody holds, with a CSV of every row.
- Upload or paste it at /verify. Every address gets a live mailbox check, and the first 100 email checks are free with a Google sign-in, no card.
How do I find email addresses at unregistered domains?
- Paste email addresses, one per line, or upload a CSV. Addresses are found anywhere in the text, so a whole export works.
- Press Find unregistered domains. Only the unique domains are sent, never the mailbox names, 20 a request: each top-level domain's RDAP server is asked for its record and DNS is checked for delegation. No mail is sent.
- Read each row: Looks unregistered, Registered, Couldn't tell or Ending doesn't exist, with how the answer was reached.
- Take the unregistered rows off the list, download the CSV, and hand the rest to the mailbox check.
Example
- You enter
- Four addresses:
jane@acme.example(registered),tom@globex.example(no registry record and no DNS),ana@initech.example(an ending whose registry gives no RDAP) andbo@umbrella.invalid(an ending that doesn't exist). - You get
- jane: Registered. tom: Looks unregistered, so it will bounce. ana: Couldn't tell, never shown as unregistered. bo: Ending doesn't exist. Download the CSV.
- Limits
- Up to 100 unique domains a run without an account and 500 when signed in with Google. 20 domains a request; registry RDAP plus a DNS check, nothing is emailed.
How does it tell that a domain is unregistered?
It asks the top-level domain's own RDAP server for the domain's record, then checks DNS for nameserver delegation. Only when the registry has no record and the name isn't delegated does the row say Looks unregistered. If the ending publishes no RDAP, or the registry doesn't answer, the row says Couldn't tell, never unregistered.
This is the same check the bulk domain availability checker runs on a list of names, applied to the domain behind each address.
Why does an unregistered domain matter on an email list?
Mail can only be delivered to a domain that exists in DNS. When a company lets a domain lapse and nobody picks it up, every address at it bounces. A list of thousands of addresses has far fewer unique domains, so this is a cheap check to run before you send.
A lapsed domain can also be registered by someone new, so an address that works today at a freshly re-registered domain may not belong to the same company. Registered does not mean the same owner.
What do you do with the flagged rows?
Take them off the send list. For domains with a registry record, the registrar and expiry date are in the CSV, and the bulk email domain expiry checker shows which are close to lapsing.
Before you email anyone on the rest, verify the addresses.
Who uses this tool, and for what?
- Marketers
- Drop addresses at lapsed domains before an import.
- Sales teams
- Skip leads whose company domain nobody holds any more.
- Agencies
- Flag client-list addresses at domains that have lapsed.
- Developers
- Triage a signup export for addresses at domains that don't exist.
What can’t this tool tell you?
- Reads the domain, never the mailbox: a registered domain says nothing about a particular address.
- Unregistered is shown only when the registry has no record and the name is not in DNS; anything else is Registered or Couldn't tell.
- Endings whose registry publishes no RDAP always show Couldn't tell.
- Up to 100 unique domains a run without an account, 500 signed in; a daily limit on free lookups can apply.
Common questions
- How do I find email addresses at unregistered domains?
- Paste the list into a bulk email domain availability checker like this one. It reads each address's domain and asks the registry and DNS whether anyone holds it.
- Is this bulk email domain availability checker free?
- Yes. It is a free tool: up to 100 unique domains a run with no account, and up to 500 a run when you sign in with Google, with no card. A daily limit on free lookups can apply.
- Does it tell me whether the mailbox exists?
- No. It checks the domain, not the mailbox. A registered domain can still hold a closed mailbox.
- Can I buy a domain that shows as unregistered?
- The row says the registry has no record and DNS agrees. The registrar confirms whether the name can be bought, and this tool does not check price or availability for sale.
- Why does a row say Couldn't tell?
- The ending publishes no RDAP, or the registry didn't answer in time. The tool never shows such a name as unregistered.
- Does it send an email to the domain?
- No. It reads registry records and public DNS. It never connects to a mail server.
Sources
A tidy list can still be full of dead addresses.
Extracting, deduplicating and syntax checks all work on the text of an address. None of them can tell whether the mailbox exists. Only the server that hosts it can answer that, through an SMTP check, and that is what the paid product 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
- Small list? Starter at $9/mo covers 2,500 emails a month, cancel anytime
Plans from $9 a month, 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.