Sometimes results surprise people. Usually they are correct — here is what is likely going on.
Lots of "risky" results
This is normal, especially for business contacts. Many companies accept every address sent to them (a catch-all), which means we cannot be 100% sure a single mailbox exists. See "What is a catch-all address?".
Some "unknown" results
Unknown means a mail server was slow or unavailable when we checked — not that the address is bad. Try checking those again a little later.
A good-looking address marked do-not-send
The address may be a throwaway, or the mailbox may simply no longer exist. Each result shows a plain-English reason — read that to see exactly why.
Tip
Every result includes a reason and a confidence score. When something surprises you, the reason almost always explains it.
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If you still have a question, we are happy to help.