What it means
Unknown is used when validation cannot reach a definitive result, such as temporary DNS or SMTP uncertainty, provider blocking, or budget guardrails.
All concepts
Email validation semantics
Unknown email validation result
An unknown result preserves validation uncertainty without charging or pretending the mailbox is usable.
Canonical status
unknown
Status language is backed by the shared validation result contract and product publish gates.
Quality signals
- unknown
- unknown quality
- not chargeable
Recommended actions
- Do not count as high-value
- Do not treat as valid
- Retry or review based on campaign risk tolerance
Charging behavior
Non-chargeable unknown paths should not increment consumed-credit counters. This keeps uncertain validation separate from usable lead economics.
- Credits are reserved before execution
- Only chargeable high-value validations are consumed
- Non-chargeable unknown paths are refunded, not consumed
Contract behavior
unknown is a canonical status and also the normalization fallback: empty or unrecognized provider statuses normalize to unknown rather than being guessed into another bucket. Validation summaries count unknown in its own bucket, and it is never high-value.
- Fallback for empty or unrecognized statuses
- Own bucket in validation summaries
- Never counted toward high_value
Retry and routing guidance
Because unknown often comes from temporary conditions, it is the one status where a later re-validation can genuinely change the answer.
- Re-validate after the temporary condition clears
- Suppress from sends until a definitive result exists
- Route persistent unknowns to manual review for valuable accounts
Related resources
Common questions
Should I send to unknown results?
Unknown results should not be treated as send-ready by default. Retry, suppress, or review them depending on your workflow.
Is unknown the same as invalid?
No. Invalid is a definitive failed result, while unknown preserves uncertainty. They are separate canonical statuses and are counted in separate summary buckets.
Why did my email come back unknown?
Common causes are temporary DNS or SMTP uncertainty, provider blocking, transport issues, or budget guardrails. Unrecognized provider statuses also normalize to unknown.