Email Address Validator

1. 1Paste one email address per line.
2. 2Read the verdict next to each address — problems are explained in plain English.
3. 3Press Use this to accept a suggested correction, such as gmail.com for gmial.com.
4. 4Optionally press Check mail servers to confirm each domain can receive email.

The format check follows the rules mail servers apply (RFC 5321 and RFC 5322): exactly one @; up to 64 characters before it, made of letters, digits, dots and a small set of symbols such as + and _; no leading, trailing or doubled dots; and a domain made of labels of letters, digits and hyphens with a real ending. The whole address can be at most 254 characters.

Some addresses are technically legal but rejected by most websites — quoted names such as "john smith"@example.com, IP addresses in brackets, and international characters. Those pass with a note, so you decide rather than the tool guessing.

The mail server check looks up the domain's MX records, which say where its email is delivered. A domain with no MX record can still receive mail at its own address; a domain with a “null MX” record has declared it accepts no email; and a domain that does not exist cannot receive anything. Only the domain name is sent for this lookup, never the full address.

No check can prove a mailbox exists without sending it an email. Many mail servers accept every address at a domain and bounce undeliverable mail later, and probing them address by address is unreliable and treated as abuse — so this tool deliberately stops at format and domain.

• Accept the suggested fix for obvious typos in common domains before you save a list.
• Treat a valid format as necessary, not sufficient; only a confirmation email proves an address works.
• Use the mail server check to catch domains that cannot receive email at all.
• Clean a list before importing it into a mailing tool, so bounces do not hurt your sending reputation.

• How to check an email address is valid before you send
• How to check a domain's MX records (can it receive email?)
• Why an email bounces even though the address looks valid