Can I re-run a failed verification for free?

Verifications that return Unknown in Valid Email Checker trigger an automatic credit refund. The original credit is returned to your account the moment the verification finalises. If you then re-run the same address, that new attempt costs one credit — but if it also returns Unknown, that credit also refunds. So the practical answer to "can I re-run a failed verification for free" is yes, as long as "failed" specifically means "returned Unknown."

A verification that returned anything definitive (Safe, Invalid, Disposable, Catch-All, Risky, Role, Spam Trap, Disabled, Inbox Full) consumed its credit and stays consumed. Re-running those is a normal paid verification — the engine has no way to know that you wanted a different answer and will not refund a definitive result just because you ran it again.

Why Unknown re-runs are effectively free

The Unknown refund is built into the engine, not a special re-run mechanic. Every verification that produces Unknown gets its credit back automatically. This applies whether it was the first attempt on an address or the tenth. The customer is never billed for a result that does not deliver a definitive answer.

If you take an Unknown result and retry the next day, the original credit was already refunded, the new attempt costs one credit, and the new attempt produces one of two outcomes:

• A definitive verdict — you spent one credit, you got an answer.
• Another Unknown — you spent one credit, you got it back. Net cost: zero.

So the failure mode never costs you. The upside is the chance to get a real answer on a previously-unverifiable address.

When re-running an Unknown is worth doing

• The original Unknown was caused by greylisting or rate-limiting that has likely expired. See how VEC handles greylisting.
• The original Unknown was during a high-traffic period on the recipient server; a retry off-hours may catch the server when it can respond.
• The address is high-value (a key business contact, a deliverable to a paying customer) and you need the best possible answer.
• You have time to wait a few days between attempts. Mailbox state and anti-probe windows shift on day-scale timeframes.

When re-running an Unknown is not worth doing

If the address is on a domain known to refuse all probes (some corporate setups, some government domains, some hardened anti-spam configurations), the engine has tried both providers already. Re-running tomorrow will probably also return Unknown. The address is genuinely unverifiable in advance, and the practical move is to either skip it or rely on engagement signals after the first send.

The same logic applies for greylisting servers with multi-day windows. A retry an hour later still looks unfamiliar; only a retry days later might work. For these you can build a queue: hold Unknown addresses, retry weekly, drop them after three or four attempts produced no definitive verdict.

Re-running definitive results

Re-running a definitive result is a normal paid verification. If the address returned Safe yesterday and you re-run it today, you pay one credit and you probably get Safe again. The engine does not deduplicate or cache, so you do pay for each new attempt — see what happens when I verify an email I already verified recently. That cost is usually only worth it if you need a fresh snapshot for a high-stakes send or if you suspect the prior result was affected by transient infrastructure noise.