Short answer: You are charged only for results we can actually determine. Results we could not confirm (unknown) are never charged.
Billing by result
| Result | Charged? | Meaning |
|---|---|---|
valid | Yes | The mailbox was confirmed to exist and accept mail. |
invalid (server rejection) | Yes | The server confirmed the mailbox does not exist or cannot receive mail. |
invalid (bad syntax / typo) | No | The address isn't a valid format, so there's nothing to verify. |
catch-all | Yes | The domain accepts all mail; deliverable to the domain, mailbox unconfirmed. |
role | Yes | A confirmed role address (e.g. info@, support@). |
unknown | No | We could not obtain a reliable signal. Not billed. |
disposable | No* | A throwaway / temporary address. Detection is free (*unless you run a full SMTP check on it — see note). |
The principle is simple: if we gave you a determination you can act on, it consumes a credit. If we could only tell you "we couldn't confirm this" (unknown), or the result is really a "don't send here" screen (disposable, or an address that's just badly formatted), you pay nothing. Each billable result costs exactly one credit.
*Note on
disposable: disposable detection is free, but if you explicitly request a full live SMTP check (check_smtp) on a disposable address and we complete it, that check is billed — a completed SMTP verification always takes priority over the free treatment of disposables.
Why unknown is free
Some mail systems (Apple iCloud, personal Outlook/Hotmail/Live, greylisting servers, rate-limited providers) prevent us from getting a trustworthy answer. Returning unknown in those cases is the honest outcome, and we do not think you should pay for a result we could not determine.
You're not charged twice within 24 hours
If you verify the same address again within 24 hours, the repeat check does not cost an additional credit — you're billed once per address per 24-hour window. See Am I charged again if I verify the same address twice? for details.
A note on force-refresh
If you re-verify an address with a force-refresh request (force_refresh=true), that deliberately skips all caching and the 24-hour dedup to perform a fresh live check, and is billed according to its new result. The exception is when that fresh result is itself free — for example, unknown — in which case it still costs nothing.