Check an email address’s syntax and whether its domain can receive mail, one or a list
Runs in your browser. Only the lookup you start is sent to cloudflare-dns.com or dns.google; nothing else leaves your device. Updated on 24 Oct 2026.An email address is valid when it follows the SMTP rules - at most 64 characters before the @ and 254 in all - and its domain has a mail server in DNS. This validator checks both, gives the reason when an address fails, and handles a list of up to 500 at once.
Choose One address and type the address into the box, or press Try an example.
Read the verdict under Result; a syntax problem is named with its reason.
Pause typing and the domain is looked up: its mail servers are listed with their preference.
For a list, choose A list of addresses, paste one per line, press the Check button under the list and then Copy as table.
Type an address, or paste a list, and each one gets two checks.
The first is syntax, following the practical core of RFC 5321 and RFC 5322. The part before the @ may use letters, digits, dots and the symbols the standard allows, including + and apostrophes; it cannot start or end with a dot or have two in a row, and it can be at most 64 characters. The domain needs at least two parts, each made of letters, digits and hyphens. The whole address can be at most 254 characters. When an address fails, the page says which rule it broke. Quoted local parts, IP-address domains and non-English letters are accepted with a note, because the standard allows them but many services refuse them.
The second is the domain. The page asks a public DNS-over-HTTPS resolver, Cloudflare's 1.1.1.1 or Google's 8.8.8.8, for the domain's MX records, the list of servers that accept its mail. It also recognises a null MX, the RFC 7505 record that says a domain accepts no email at all, and the old fallback where a domain with no MX receives mail at its own address. Only the domain part is sent to that resolver; the part before the @ never leaves your device.
What no validator can tell you honestly, without sending a message, is whether the mailbox exists. This page never sends a test email and never connects to a mail server. Services that claim certainty usually open an SMTP conversation and stop before the message, and many large providers deliberately answer "yes" to every address so that spammers cannot use that trick. A passing result here means the address is well formed and its domain is set up for mail, nothing more.
For a list, paste one address per line, or copied recipients such as Name [email protected]; duplicates are removed.
Paste it into the box above. The page checks the syntax against the SMTP rules and tells you which rule is broken if it fails, then asks a public DNS resolver whether the domain has mail servers. Both checks take a second, and a list of up to 500 addresses works the same way.
No, and no honest tool can without sending mail. The only way to know is to deliver a message or open an SMTP conversation with the server, and this page does neither. Many large providers also accept every address during that conversation on purpose, so even those probes often cannot tell.
An MX record is the DNS entry that names the servers accepting email for a domain, each with a preference number; lower numbers are tried first. Gmail's domain lists several. A domain with no MX record and no address record has nowhere to receive mail, so any address at it will bounce.
A null MX, defined in RFC 7505, is a single MX record with preference 0 and the host ".". A domain publishes one to say it never accepts email, so senders can fail at once instead of retrying for days. Addresses at such a domain are well formed but undeliverable.
Yes. The plus sign is one of the characters RFC 5322 allows before the @, and Gmail, Outlook and many other providers deliver name+anything@ to the same mailbox as name@. Some sign-up forms wrongly reject it, but the address itself is valid, and this validator accepts it.
Only the domain, the part after the @, goes to the public resolver you choose, Cloudflare or Google, as a DNS question. The part before the @ never leaves your device, no email is sent, and no mail server is contacted. Our own server is not involved at all.
Still stuck? Ask about Email Address Validator and anybody who knows can answer. No account needed.
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