Email Address Validator

About the Email Address Validator

Type an e-mail address — or paste a whole list from a spreadsheet, a sign-up export or an address book — and each one is checked and marked valid, risky or invalid, with the reason in plain words.

The checks follow the standards: the syntax and length limits of RFC 5321 and RFC 5322 (64 bytes before the @, 254 for the whole address), international domains converted to their ASCII form as DNS needs them, and addresses with non-ASCII names, which need SMTPUTF8 (RFC 6531). Then each domain is checked over DNS: does it exist, does it have MX records, does it publish a null MX (RFC 7505: “we accept no mail”), or does mail go to its own address (the implicit MX of RFC 5321)? Addresses at disposable providers, role addresses such as info@ or postmaster@, and typos such as gmial.com are flagged too.

No mailbox is ever contacted: nothing is sent and no mail server is asked whether an address exists, so the page cannot — and does not claim to — prove that a particular mailbox is in use.

Without a pass the result is a free preview: every count, with the verdicts and reasons of the first addresses of a list; a single address shows its verdict with the reasons and mail servers hidden. The full results, copying the addresses and the CSV unlock with a Pro pass; a list unlocks with a pass only.

Common uses

• Catching typos in a sign-up or checkout form before a confirmation e-mail bounces.
• Cleaning an exported list of contacts before importing it into a newsletter or CRM tool.
• Finding disposable addresses in trial sign-ups.
• Checking that a partner’s or customer’s domain can receive mail at all.

What each verdict means

• Valid: the syntax is correct and, with the DNS check, the domain accepts mail (it has MX records whose first server resolves).
• Risky: the address may work but often does not: a disposable provider, a role address, a likely typo, a quoted or IP-address form, a name with non-ASCII letters (SMTPUTF8), a domain without MX records, or a domain the DNS check could not reach.
• Invalid: the address cannot receive mail as written: broken syntax, too long, a domain that does not exist, a null MX, or no mail records at all.

A valid verdict does not mean the mailbox exists: only the domain’s mail server knows, and asking it (“SMTP probing”) is unreliable and abused by spammers, so this page never does it.

The rules it checks

• Syntax: the part before the @ is a dot-atom — letters, digits and the symbols ! # $ % & ' * + - / = ? ^ _ { | } ~ and the backquote, with single dots between them — or a quoted string (RFC 5321 §4.1.2, RFC 5322 §3.4.1); the domain is a host name of letters, digits and hyphens, or an IP address in brackets.
• Lengths: at most 64 bytes before the @, 255 for the domain (253 characters as written) and 256 for the whole path including its angle brackets — so 254 for the address (RFC 5321 §4.5.3.1); each part of a domain name at most 63 characters.
• International addresses: domains are converted to their ASCII (Punycode) form for DNS; a non-ASCII name before the @ needs SMTPUTF8 on every server on the way (RFC 6531).
• Mail records: MX records first; with none, RFC 5321 §5.1 treats the domain’s own address as an implicit MX; a single MX of “.” is a null MX: the domain accepts no mail (RFC 7505).

Disposable, role and typo checks

• Disposable providers come from the community-maintained disposable-email-domains list (CC0), built into this page; subdomains of a listed domain count too.
• Role addresses are the shared mailboxes of RFC 2142 — postmaster, abuse, webmaster, info, sales, support and others — plus common ones such as admin@, noreply@ and hello@. They reach a team or a robot rather than one person.
• Typos are names a letter or two away from a large provider (gmial.com, hotmial.com, yaho.com) and slips in a .com, .net or .org ending (.con, gmail.co). A provider’s real country domain, such as hotmail.de or yahoo.ie, is never “corrected” into another one.

Limitations

• Up to 500 addresses per run; split longer lists.
• It does not contact mail servers, so it cannot tell whether a particular mailbox exists, is full or has been closed.
• The disposable list is a snapshot of a community list built into the page: new throw-away services appear all the time.
• Typo suggestions cover large providers only; for other domains the DNS check shows whether the domain can receive mail.

Privacy

Sends data to online services

The addresses are checked in your browser. With the DNS check on, only the domain names (the part after the @) are sent, as DNS questions without cookies, to a public DNS-over-HTTPS resolver (a second one if the first cannot be reached). MySmartCoPilot does not receive or store your list.