How to Find Email Addresses at Unregistered Domains in a List
To find email addresses at unregistered domains, ask each address's registry whether it holds a record for the domain, then check DNS. The bulk email domain availability checker does both for every address in a pasted list or CSV and gives each one a row: Looks unregistered, Registered, Couldn't tell or Ending doesn't exist.
A domain is shown as unregistered only when the registry has no record and DNS agrees. The check reads the domain, not the mailbox.
Where unregistered domains come from
Companies close, merge and let domains lapse, and old signups and purchased lists keep the addresses. When nobody picks the domain up, every address at it bounces. A list of thousands of addresses has far fewer unique domains, so checking by domain is cheap.
The by-hand way
- Take the domain after the @, for example
acme.examplefromsam@acme.example. - Find the registry for its ending in IANA's RDAP bootstrap file and ask it for the domain's record.
- Check whether the domain has nameservers in DNS.
- No record and no nameservers means nobody holds it. Repeat for every unique domain.
For the same check on a list of names you might want to buy, see check if a domain is really available.
Step 1: paste the addresses
Paste addresses one per line, or upload a CSV. Only the unique domains are sent, never the mailbox names, 20 a request.
Step 2: run the check
Press Find unregistered domains. Each ending's RDAP server is asked for the record and DNS is checked for delegation. No mail is sent.
Step 3: read the result
| Result | What it means |
|---|---|
| Looks unregistered | No registry record and no DNS; mail will bounce |
| Registered | The registry or DNS shows the name is held |
| Couldn't tell | The ending has no RDAP, or the registry did not answer; never shown as unregistered |
| Ending doesn't exist | The top-level domain is not real |
The CSV carries the registrar and expiry date for registered domains. Unregistered rows are left out of the list handed on to the mailbox check.
What this check cannot do
- It checks the domain, not the mailbox.
- A name is shown as unregistered only when the registry and DNS agree.
- It does not check price or whether the name can be bought.
- Up to 100 unique domains a run without an account, 500 signed in; a daily limit on free lookups can apply.
For bare domains use the bulk domain availability checker.
Next: the rest of the list
For the addresses that remain, use the verify page: the first 100 checks are free with a Google sign-in, no card.
Try it now
Paste your list into the bulk email domain availability checker at simpleverifier.com.
Common questions
How do I find email addresses at unregistered domains?
Take the domain after the @ in each address and ask its registry whether it holds a record, then check DNS. A bulk email domain availability checker does both for every address in a pasted list.
How does it tell that a domain is unregistered?
The registry's RDAP server has no record and the name is not delegated in DNS. If the ending has no RDAP, or the registry does not answer, the row says it could not tell.
Will an address at an unregistered domain bounce?
Yes. Mail can only be delivered to a domain that exists in DNS.
Can a lapsed domain be registered by someone else?
Yes. An address that works at a re-registered domain may not belong to the same company. Registered does not mean the same owner.
Does the check tell me whether the mailbox exists?
No. It checks the domain, not the mailbox.
Check your list before you send
Real mailbox checks over SMTP, and nothing is sent to the address. Sign in with Google and your first 100 email checks are free, no card. Plans for bigger lists are on the pricing page.