Why is a result unknown?

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A result is unknown when the mail server for the address does not give a clear answer. Common reasons:

• The server is busy or asks us to try again later (greylisting)
• The server timed out
• The server blocks verification requests

Unknown results never use a credit. In lists, the credits held for unknown results go back to your balance when the list finishes.

Try the address again in a few hours. Many unknown results become valid or invalid on a second check.

Actualizado el 30 oct 2026