Email domain checker
Paste an address or a domain. We confirm the domain exists and can receive mail, and flag throwaway, free and misspelled domains before they reach your list.
The five checks, and what each one catches
A domain check runs before any mail server is contacted, which makes it fast and safe to run on a sign-up form. It catches the addresses that can never work, whoever the person behind them is.
| Check | How we run it | What a failure means |
|---|---|---|
| Domain exists | NS lookup; NXDOMAIN means no such name | Typo, lapsed domain or invented address |
| Mail servers | MX lookup, each host resolved; A-record fallback | Nowhere to deliver: every address bounces |
| Null MX | A single MX of priority 0 pointing at "." | The owner declares the domain takes no mail |
| Disposable | Match against our disposable-domain list | Throwaway inbox, gone within hours |
| Free provider | Match against common consumer mail domains | Personal inbox, flagged not failed |
Null MX per RFC 7505; A-record fallback per RFC 5321 section 5.1.
Domain checks on a sign-up form
Three kinds of bad sign-up fail at the domain. Someone types gmial.com, invents a company domain that doesn't exist, or grabs a disposable address to get past the form. Each one lands on your list and bounces on the first send.
You can catch all of them before the form submits. Run the domain check the moment the person leaves the field, show the typo suggestion, and block throwaway domains. The real-time verification API does this and the mailbox check in one call.
Pair it with a syntax check for the part before the @, and you've stopped every address that could never deliver.
Typos the checker flags
A typo in the domain is the most fixable bad address there is. The person is real and wants your mail; they just hit the wrong key. The checker compares the domain with the big consumer providers and flags anything one or two characters away.
You'll see it on gmial.com, hotmial.com, yaho.com and outlok.com. Some of those typo domains are registered and even accept mail, so a DNS check alone can pass them. That's why the flag is separate from the MX result: show the suggestion to the person and let them confirm.
From a working domain to a working mailbox
A domain that passes can still hold dead mailboxes. People leave jobs, and their addresses start returning a 550 while the company's MX records stay perfect. That's the gap between domain validation and mailbox validation.
ZapBounce closes it with its own SMTP check on port 25, stopping before DATA so nothing is sent. Every address comes back valid, invalid, catch-all or unknown, and unknowns are never billed. On the pricing page, 1,000 checks cost $5 with no minimum and no expiry.
Questions people ask
How do I check if an email domain is valid?
Check three things: the domain exists in DNS, it publishes MX records (or at least an A record senders can fall back to), and it is not a null MX that refuses all mail. This tool runs all three live and adds disposable, free-provider and typo flags.
Can a domain exist but still not receive email?
Yes. A registered domain with no MX and no A record has nowhere to deliver mail, and a domain with a null MX (a single MX record pointing at ".") says outright that it accepts none. Every address at either kind of domain hard-bounces.
Does a valid domain mean the email address is valid?
No. The domain check tells you mail can arrive at the domain. Whether the mailbox before the @ exists is a separate question, answered by an SMTP check at the RCPT TO step. The email verifier on this site runs that check.
What is a disposable email domain?
A domain run by a throwaway inbox service such as Mailinator or Yopmail. Anyone can read the inbox, and addresses stop being used within hours. They are real domains that receive mail, which is why a DNS check alone passes them and a list match is needed.
Check the mailbox, not only the domain
Verify every address on your list with 100 free checks a month, no card, and no charge for unknowns.