Runs entirely on this site — no third-party verification API, nothing leaves your list except the domain names looked up.
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Address
Verdict
Findings
Mail provider
How to read the verdicts.
Valid
Well-formed, domain resolves to a mail server, no red flags. Safe to send. (A specific mailbox can still bounce — only the receiving server knows that.)
Risky
Deliverable domain but something to look at: probable typo with a suggestion, role account, disposable domain, or a domain with no MX record that only answers on a web address.
Invalid
Malformed, or the domain does not exist / explicitly refuses mail. Remove these.
Duplicate
Same mailbox appears earlier in the list (Gmail dots and +tags are treated as the same box).
Domain lookups run through a small function on this site and are cached in your browser for seven days. Disposable-domain and typo lists are built in and can be extended in the page source.