Email checker: verify an email address
Check one email address before you send to it or store it: syntax, typos, whether its domain takes mail, disposable services, role addresses and Gmail’s own rules, then a live check with its mail server.
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How the email address checker works
The email address checker looks at one address before you rely on it: its syntax, its domain and the mail server behind it. Use it before you add an address to a list or send something important to it.
How to read the summary
- Isn’t a valid email address or can’t receive email: the syntax is wrong, the domain or its top-level domain doesn’t exist, or the domain refuses all mail or has nowhere to deliver it. The mail server isn’t asked.
- A warning: a disposable service, a likely typo, a domain with no MX record, or a role address such as info@. The live check is still offered, except for disposable addresses.
- Passes the basic checks: nothing wrong was found. Whether the mailbox exists is left to the live check, whose answer is a hint.
- Some checks didn’t finish: a DNS or list lookup failed, so the result is incomplete, not bad.
What the live check’s answers mean
The live check asks the domain’s most preferred mail server that has a public IPv4 address, trying up to three, or the domain’s own address when it has no MX record. It runs on its own right after you submit the form, but not when a shared link or a reload opens the page; then use Run live check. Finding the mail server may take at most 8 seconds and the SMTP conversation at most 35; a check stopped before the mail server was asked doesn’t count toward the daily 5. Its answer updates the summary at the top:
- Accepted: the server took the address at
RCPT TO. Some servers accept there and bounce the message later. - Rejected: a permanent answer that the mailbox doesn’t exist or is disabled, such as
5.1.1. - Accepts any address: a made-up address was accepted too, so this one can’t be confirmed.
- Couldn’t tell: a temporary code (often greylisting), a refusal for policy, reputation or a blocklist, or a server that hung up, none of which says anything about the mailbox. A full mailbox is reported here too.
Typos it can catch
A domain one or two keystrokes from a popular provider gets a suggested fix. When a domain doesn’t exist, the checker also asks whether its top-level domain exists, and tries the likely correction of a mistyped ending such as .con, suggesting it only if that domain accepts mail.
What to check next
To grade the sending setup of a whole domain, use the deliverability score. The disposable email check screens a whole list for throwaway domains, and the data leak check shows whether an address appears in known data leaks.
Updated · Maintained by Liviu Tanase
Questions
What does the checker test?
Syntax against the email standards (RFC 5321 and 5322, including the 64-character limit before the @ and 254 overall); whether the domain exists and has mail servers, including null MX (RFC 7505) and domains with no MX record; typos in popular providers (gmial.com) and in endings that don’t exist (.con); the open-source lists of more than 100,000 disposable email domains; role addresses such as info@ and noreply@; Gmail’s username rules; and which provider runs the mailbox. Unless the address is invalid or disposable, a live SMTP check asks the domain’s mail server whether it accepts the address, up to 5 times a day.
Can it tell whether the mailbox exists?
Sometimes, and often wrongly. The live check connects to the domain’s mail server on port 25 from Cloudflare’s network and stops after RCPT TO, so no email is sent. Many servers accept every address at that point, refuse or delay checks from cloud networks, or answer differently each time, so its answer is a hint, not a verdict. It also tries a made-up address at the same domain to spot servers that accept everything. For an accurate result, including spam traps and abuse addresses, validate with ZeroBounce.
Where does the address go?
The first checks run on this page. DNS questions about the domain go from your browser to Cloudflare’s public resolver, or Google’s as a fallback, and the disposable-list match happens in your browser. The live check sends the address to zerobounce.ai, which repeats those checks and asks the domain’s mail server. Neither the address nor the server’s answer is kept; your IP address is kept as a counter for the daily limit until the next day. The address is also put in the page link so you can share the result.
Why only 5 live checks a day?
Each one opens a real connection to someone’s mail server, and mail providers block networks that make many of them. So the live check is limited to 5 per network a day and 300 a day for everyone. Invalid and disposable addresses are never checked live and don’t count. A check that couldn’t run doesn’t count either.
Why is a role address flagged?
Addresses such as info@, sales@ or noreply@ reach a team, a system or nobody, not one person. They are fine for business contact. Many senders keep them off marketing lists, because nobody in particular signed up and more than one person reads them.
Do dots and plus signs matter in Gmail addresses?
Not for gmail.com. Google ignores dots in Gmail usernames and delivers jane+news@gmail.com to jane@gmail.com, so the checker shows the mailbox an address really reaches, which helps spot duplicate sign-ups. Work and school accounts on their own domains keep their dots. Most large providers, including Microsoft 365, also accept +tags.
Why warn about a typo when the domain exists?
Domains one keystroke away from big providers, such as gmial.com or hotmial.com, are often registered to collect mail meant for someone else. An address there is far more likely a slip than a real mailbox, so the checker suggests the likely fix.
Why does it link to ZeroBounce?
zerobounce.ai is run by Hertza L.L.C., the company behind ZeroBounce, an email validation service. The checks here are free but limited, and the live check is often wrong; ZeroBounce, our paid service, validates the mailbox itself. The link carries a referral code.
How do I check if an email address exists without sending an email?
Enter it above. After the syntax and DNS checks, the live check connects to the domain’s mail server on port 25, introduces itself (EHLO), names a sender (MAIL FROM) and asks about the address (RCPT TO), then says QUIT. It never sends DATA, so no message is delivered. The answer is Accepted, Rejected (a permanent “no such mailbox” such as 5.1.1), Accepts any address or Couldn’t tell. If mail to the address already bounced, paste the bounce into the bounce explainer to read its codes.
What does “accepts any address” (catch-all) mean?
Some mail servers say yes to every address at their domain and sort out later which ones are real, so a yes proves nothing. When the address is accepted, the checker asks the same server about a made-up address at the same domain (tanase-check- and 16 random hex characters). If that is accepted too, the result is Accepts any address: the server can’t tell you whether this mailbox exists. To review the whole domain’s mail setup, use the deliverability score.
Can I check a whole list of email addresses?
Not here: this checker takes one address at a time, and its live check runs at most 5 times a day per network. The disposable email check has a list tab that screens a whole file for throwaway domains, typos, role addresses and domains that can’t receive mail. To check every mailbox on a list, use an email validation service such as ZeroBounce.