Email Address Validator
Instantly check whether an email address matches a practical RFC 5322-style format, and verify whether its domain can actually receive mail (MX record lookup). Free tool for form validation and mailing list cleanup.
Email format verdict examples
| Example address | Verdict | Reason |
|---|---|---|
| [email protected] | Valid | Basic format (local part @ domain part) |
| [email protected] | Valid | Tagged address using a period and a plus sign |
| [email protected] | Invalid | Two consecutive periods in the local part |
| @example.com | Invalid | The local part (before "@") is empty |
| user@example | Invalid | The domain has no top-level domain (e.g. .com) |
| user example.com | Invalid | No "@" symbol is present |
Usage tips
- Even a correctly formatted address like "[email protected]" is not guaranteed to actually receive mail — the MX record check below gives you a rough idea of that.
- When cleaning up a mailing list, it is efficient to first filter out obvious typos with the format check, then confirm the domain itself is valid with the MX record check.
- Major domains like Gmail and Outlook always have MX records, but a company's own domain may lack them right after setup or due to a misconfiguration.
- A stray trailing space left over from copy-pasting an address can cause the format check to fail — watch for extra whitespace around the input.
- If you want real-time validation in your own signup form, the practical regular expression discussed in the side note below can be reused directly.
Frequently asked questions
Side Note — why email validation happens in two stages
Email validation is easier to understand once you split it into two distinct layers: format and existence. The format check is a purely static test of whether a string has the right shape (local part, @, domain part) and never touches the network. Confirming existence, on the other hand, requires a DNS lookup against the domain, which a browser cannot perform directly from JavaScript — it has to happen on the server. This tool splits the two into separate steps precisely because they are technically different kinds of checks.
RFC 5322 defines the formal grammar for email addresses, and it is surprisingly intricate. For example, quoting the local part in double quotes legally permits spaces and consecutive periods that no real-world mail server would ever actually use. Because of this, most practitioners skip a fully compliant parser in favor of the simplified regular expression defined by WHATWG's HTML Living Standard, and this tool follows the same pragmatic approach.
An MX record is a DNS entry that says which mail server should receive mail for a given domain, and lower preference values are tried first. When a company migrates its mail infrastructure, it is common to keep several MX records active at once during a gradual cutover. If no MX record exists at all, mail sent to that domain is very likely to be rejected by the receiving side.