Temporary Unreachable Emails
“Temporary Unreachable” is a separate class from invalid. It typically means a verifier could not obtain a reliable signal due to transient behavior like greylisting, throttling, or network timeouts.
Common causes
- Greylisting: server asks the sender to retry later
- Rate limiting: verification bursts get throttled
- Timeouts: slow SMTP responses or network instability
- Temporary mail server issues: transient outage or overload
Why not mark as invalid?
Because a transient failure is not proof the mailbox does not exist. Treating this class as invalid can over-suppress leads and reduce coverage unnecessarily.
Recommended handling approach
| Outcome | Interpretation | Typical action |
|---|---|---|
| Temporary Unreachable | Signal unavailable at time of check. | Retry later / revalidate on a schedule. |
| Repeated Temporary Unreachable | Provider repeatedly blocks reliable signal. | Increase interval, reduce concurrency, or downgrade confidence. |
| Clear invalid evidence | Mailbox does not exist / hard fail. | Suppress from export. |
FAQ
Is Temporary Unreachable the same as invalid?
No. It indicates the verifier could not reliably confirm deliverability due to transient behavior (timeouts, throttling, greylisting). It does not necessarily mean the mailbox is invalid.
What causes Temporary Unreachable?
Common causes include greylisting, rate limiting, temporary server issues, network timeouts, or policies that reduce reliable signal during verification.
What is the best strategy?
Treat it as a separate class: retry later, revalidate on a schedule, and avoid permanently suppressing unless repeated evidence suggests invalidity.
Why does documentation matter?
Because buyers need predictability. Clear definitions help users interpret outcomes and set expectations for deliverability and list maintenance.