Email verifier

What each result means

• Invalid format means the cell is not everyday email syntax.
• Domain check passed means MX records were found. That does not prove a mailbox exists.
• Mailbox not verified is the default after local checks. Syntax and DNS never claim an inbox exists.
• Unable to check means DNS or an optional provider lookup timed out, failed, or was inconclusive.
• Example address, disposable-domain match, and possible domain issue come from local lists. The address is not rewritten.
• Optional Advanced mailbox check uses Abstract only when ABSTRACT_EMAIL_API_KEY is set and you choose that action.

What leaves the browser

The CSV is parsed on this device. Syntax, typos, duplicates, and the disposable list stay local. A domain check sends domain names only to this site for DNS. Advanced mailbox verification is optional and sends email addresses only if you run that action and a server API key is configured. Other columns are never included.

Limitations

• Core email checks work without paid APIs. CSV cleaning elsewhere on the site also works without API keys.
• Domain DNS needs a network path from the host. Failures show as Unable to check, not Invalid format.
• ABSTRACT_EMAIL_API_KEY is optional. Without it, Advanced mailbox check stays hidden and local results continue.
• This tool does not send mail to the addresses in your file.