What makes an email address valid
The parts of an email address, the rules this checker enforces, and why format validation cannot prove an inbox is real.
The anatomy of an address
Every email address has two parts joined by a single @ sign. The local part on the left identifies the mailbox and may contain letters, digits and a set of symbols including dots, plus signs, hyphens and underscores. The domain on the right is a series of dot-separated labels ending in a top-level domain such as com, org or co.uk. This tool requires exactly one @, a non-empty local part, at least one dot in the domain, and a final TLD of two or more letters, which together describe the vast majority of real addresses.
The rules this checker enforces
Beyond the basic shape, a few extra rules catch addresses that look plausible but would bounce. Whitespace anywhere makes the address invalid, since real addresses do not carry unquoted spaces. The local part cannot start or end with a dot or contain two dots in a row. Length is capped at 254 characters overall and 64 for the local part. Deliberately, the checker uses a practical rule rather than the full RFC 5322 grammar, so rare quoted or bracketed forms are treated as invalid because ordinary mail flows never use them.
Typos versus invalid syntax
A misspelled domain like gmial.com is a different problem from a malformed address. The syntax is perfectly legal, so the format check passes, yet the mail would never reach Gmail. That is why this tool runs two independent steps: a format test that returns valid or invalid, and a typo scanner that compares the domain against a list of common provider misspellings and bad endings. When it finds one, it offers a corrected address that only changes the domain and leaves your local part, including any plus tag, untouched.
Why format checks cannot confirm delivery
Passing this validator means the address is shaped correctly, not that someone reads it. Confirming a real inbox requires steps this tool does not take, such as an MX record lookup to find the mail server, an SMTP probe, or the industry standard of sending a confirmation link the owner must click. Use format validation to catch obvious mistakes in a signup form or a mailing list before they cause bounces, then rely on a real confirmation email to prove the address works.