Unknown email results: uncertainty stays visible

An unknown email verification result means a conclusive mailbox outcome could not be established. It does not automatically mean invalid. RefreshList keeps these records separate from valid exports and charges one credit for each completed unique unknown check because verification work was performed even though the evidence remained inconclusive.

Last updated 2026-09-14. Read the scope and limitations before applying a result.

Key points

Unknown is not converted to valid.
Unknown checks are chargeable.
Duplicates remain free.

Detailed explanation

Some receiving systems do not disclose enough information. Repeating checks does not guarantee a different outcome; review the reason and later first-party evidence.

Example

85 valid, 10 invalid, and 5 unknown checks consume 100 credits, not 95.

How RefreshList handles it

Unknowns have a separate download. Only unprocessed reservations are returned; completed unknown checks are not unprocessed.

Limitations

No artificial confidence percentage is added. Rechecks can remain inconclusive.

Methodology and sources

Product behavior is described from the current RefreshList implementation and provider contract. Protocol context should be checked against the applicable standards and provider documentation. This page does not create a benchmark or certification.