Bulk verification
For the list you inherited, the export before a migration, or the file somebody bought two years ago and nobody has touched since.
What a B2B list usually looks like coming back
- valid
- 71,40271.4%
- invalid
- 12,88112.9%
- catch-all
- 9,7309.7%
- unknown
- 5,9876.0%
Unknown means the server would not give a straight answer. We report it, and we do not bill it.
The shape a typical list takes, not a measured ZapBounce result. The catch-all share reflects the roughly 28% reported for B2B lists.
How a job runs
Upload the file
CSV, TXT or a spreadsheet export. We read the column that holds addresses and leave the rest of your columns alone, so what you download still matches what you uploaded.
We deduplicate first
Duplicates inside one upload are collapsed before anything is checked, and you are not charged twice for the same address. Most inherited lists lose several percent here.
Each address is checked
Syntax, then the domain's mail servers, then the SMTP conversation, then a catch-all probe. Greylisted domains get a retry rather than a guess.
Download everything
Every address comes back with its result, a reason code, the MX host we spoke to and the server's literal reply, so a result you disagree with can be audited rather than argued about.
What you are charged for
| Situation | Billed? |
|---|---|
| Valid or invalid verdict | Yes, one credit |
| Catch-all domain | Yes, one credit, because the finding is real |
| Unknown | No |
| Duplicate within the upload | No |
| Row that isn't shaped like an address | No |
| Job that fails on our side | No, the batch is refunded |
Prices run from $5 for 1,000 addresses. Credits never expire.
What a clean list still cannot tell you
Questions about bulk jobs
What file formats can I upload?
CSV, TXT and spreadsheet exports. If your file is unusual, send it and we will tell you whether it needs changing before you spend credits.
How fast is it?
Most of the wait is other people's mail servers rather than us. Greylisted domains take longest because the honest handling is to retry rather than guess.
What happens if I run out of credits mid-job?
The job pauses rather than failing. Top up and it resumes from where it stopped, and nothing already verified is charged again.
Do you keep my list afterwards?
Until you delete the job. Delete it and the addresses, verdicts and reasons all go with it.
Run a sample first
100 free checks a month. Send a few hundred and count what comes back unresolved.