Email validator for sign-up forms, mailing lists and CRM imports
This email validator checks whether an address is correctly formed according to the practical rules of RFC 5321 and RFC 5322 — local part up to 64 characters with no leading, trailing or doubled dots, a domain made of valid labels with a real top-level domain, and a total length under 254 — and then goes further: it spots typos in popular domains (gmial.com, hotmal.com, .con), flags disposable providers such as Mailinator and Yopmail, identifies role accounts like info@ or admin@, and handles internationalised domains by showing their Punycode form.
Paste a whole list in bulk mode to validate up to 2,000 addresses at once, see a results table with the reason for every warning or failure, copy only the usable addresses, or export everything to CSV. All of this happens in your browser; the addresses are never uploaded. An optional MX lookup, off by default, asks Google Public DNS whether the domain can receive mail.
How to use the Email Validator
- Type an address in “Email address”. The result and the detailed checks update as you type; click “Use it” on a typo suggestion to accept the fix.
- Switch to “Bulk list”, paste one address per line (names in angle brackets such as
Jane <jane@x.com>are fine) and press “Validate all”. - Review the table: Valid, Warning (deliverable but worth a look — disposable, role, typo, duplicate) or Invalid with the exact reason.
- Tick “Look up MX records” if you want to confirm the domains have mail servers. Only the domain names are sent to dns.google.
- Use “Copy valid only” to grab the cleaned list or “Export CSV” for a spreadsheet.
Email Validator features
Real RFC rules, practical interpretation
Checks local-part characters and length, dot placement, quoted strings, domain labels, hyphens, numeric TLDs and the 254-character limit — matching what mail servers actually accept.
Typo correction
Damerau–Levenshtein distance against 38 of the most common mail domains plus TLD slips such as .con and .cmo, with a one-click fix.
Disposable and role detection
A built-in list of around 100 temporary-mail domains and 50 role mailbox names, so you can decide how to treat them.
IDN and Punycode aware
Addresses like müller@bücher.example are validated and shown in the xn-- form the mail system uses.
Bulk mode with CSV export
Up to 2,000 addresses per run, duplicate detection, a summary and a downloadable CSV with notes for each row.
Optional MX check
Opt-in lookup through Google Public DNS over HTTPS, with graceful handling of domains that have only an A record or do not exist.
What makes an email address valid?
An address is local-part@domain. RFC 5322 allows the local part to contain letters, digits and the characters ! # $ % & ' * + / = ? ^ _ ` { | } ~ -, with dots between (not at the ends or doubled). Anything else — including spaces — must be inside double quotes, a form so rarely supported that this tool marks it as a warning. RFC 5321 limits the local part to 64 characters and the whole forward path to 256, which in practice leaves 254 for the address.
The domain follows host-name rules: labels of 1–63 letters, digits or hyphens, not starting or ending with a hyphen, separated by dots, with a top-level domain of at least two letters. Unicode domain names are converted to Punycode (xn--…) before being sent, which the tool does with the same algorithm your browser uses for URLs.
Format checks versus deliverability
Only sending a message and getting it read truly proves a mailbox exists. Everything a validator can do falls short of that, but each layer removes a class of problems:
| Check | What it catches | What it cannot know |
|---|---|---|
| Syntax (this tool, offline) | Typos, missing @, bad characters, impossible domains | Whether the mailbox exists |
| Typo suggestions | gmial.com, hotmal.com, .con — the most common data-entry errors | Deliberate but unusual domains |
| Disposable / role lists | Throwaway inboxes and shared mailboxes | New disposable domains not yet listed |
| MX lookup (opt-in) | Domains with no mail server or that do not exist | Whether the specific user exists |
| SMTP probe (not done here) | Some servers reveal unknown users | Catch-all domains; many servers refuse to answer and probing can get senders blocked |
Tips for cleaner email lists
- Validate at the point of entry and show the typo suggestion to the user — accepting a corrected domain fixes most bounces before they happen.
- Treat role accounts and disposable addresses according to your purpose: fine for a receipt, risky for a marketing list where bounces and complaints hurt your sender reputation.
- Remove duplicates case-insensitively; the domain part is case-insensitive everywhere, and in practice so is the local part at nearly every provider.
- Need to pull addresses out of a messy document first? Use the Email Extractor, then paste them here. For deeper DNS detail (SPF, DMARC, MX priorities) try the DNS Lookup.
Email Validator FAQ
Is this email validator private?
Yes. Syntax checks, typo detection and the disposable and role lists all run inside your browser, and nothing is stored. The only network request is the optional MX lookup, which sends just the domain name (never the full address) to Google Public DNS.
Can an email validator confirm that an address really exists?
No tool can do that reliably without sending mail. This validator confirms the format is correct and, if you enable it, that the domain has mail servers. Many servers accept every address (catch-all) or refuse to say, so the final proof is a delivered message.
Why is a valid-looking address flagged as a warning?
Warnings are for addresses that are deliverable but worth attention: a likely typo in the domain, a disposable provider, a role mailbox such as info@, a quoted local part, or a duplicate in bulk mode.
Does the validator support international (non-English) email addresses?
Domains with Unicode characters are fully supported and shown in Punycode. Non-ASCII characters in the local part require SMTPUTF8 support on both servers, so they are flagged as a warning rather than accepted silently.
How many addresses can I validate in bulk?
Up to 2,000 per run, instantly. With MX lookup enabled, the first 200 distinct domains are queried to keep the run fast and polite to the DNS service.
Is a 255-character email address valid?
Not in practice. RFC 5321 limits the forward path to 256 characters including the surrounding angle brackets, leaving 254 for the address itself, and the local part may not exceed 64.