Email verification · comparison
Kickbox alternative
Open source verification with the evidence attached.
What Kickbox is
Email verification with a deliverability focus, sold per verification with a well-regarded API.
A clean API and a long track record. Their Sendex score is a genuinely useful signal that we do not attempt to reproduce.
Pick Kickbox when: You want a managed API with support behind it and quality scoring beyond existence.
You want to see the SMTP transcript behind every verdict, or you need the list to stay on your own hardware.
Side by side
| Kickbox | Verdict | |
|---|---|---|
| Where it runs | Their servers | Yours |
| Evidence | Score and label | Raw reply and status code |
| Source code | Closed | MIT |
| Free tier | Trial credits | Unlimited, self-hosted |
Kickbox charges per verification. Free and MIT, or $59/mo hosted.
The honest summary
Verdict has no contact database and does not send campaigns. It opens an SMTP connection to the receiving server, asks whether the mailbox exists, and reports what the server said. When the server refuses to answer, or the domain accepts every address, it says so instead of guessing. That is the whole product, it is MIT licensed, and it runs on your own machine so the list never goes anywhere.
Try it on a real list
Paste up to 500 addresses. Free, no signup, nothing stored. The fairest test is your last campaign's bounce list, since you already know which ones failed.