Articles on: Email List Verification

Verification results: All possible states and reasons

Verifying a list of emails will return results on the email addresses, each email address is given a state that represents the overall quality and deliverability of the email.

There are 5 states that can result from the verification process.

Below is a breakdown of these states (Deliverable, Undeliverable, Risky, Unknown, and Duplicate) and a list of the possible reasons for these results.

Deliverable - We can determine with a high level of confidence that the email address is associated with a valid account.

Possible reasons for Deliverable emails:
Accepted Email: The email address exists and is deliverable.

Undeliverable - We can determine with a high level of confidence that the email address is not associated with a valid account.

Possible reasons for Undeliverable emails:
Invalid Email: The email address does not pass syntax validations.
Invalid Domain: The email address domain does not exist, is not valid, or should not be mailed to.
Rejected Email: The email address was rejected by the mail server because it does not exist.
Invalid SMTP: The mail server returned an unexpected or invalid response.

Risky - Emails seem to be deliverable but should be used with caution due to low quality or deliverability.

Possible reasons for Risky emails:
Low Quality: The email address has quality issues that may make it a risky or low value address.
Low Deliverability: The email address appears to be deliverable, but deliverability cannot be guaranteed.

Unknown - The domain associated with the email address is not responding, meaning we cannot determine the validity of the email account.

Possible reasons for Unknown emails:
No Connect: Could not connect to mail server.
Timeout: Mail server session or DNS query timed out.
Unavailable SMTP: The mail server was unavailable to process our request at this time.
Unexpected Error: An unexpected error occurred.

It's important to note that some Unknown emails are the result of greylisting. These will be retried automatically, usually within a few minutes, and the results will be updated when possible.

Duplicate - The list contains more than one of the same email.

If you have additional questions about verification results, don't hesitate to reach out to our support team via chat or

Updated on: 04/05/2023

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