Spaw vs Kickbox
Kickbox is an email verification API that returns deliverable, undeliverable, risky or unknown plus a 0 to 1 Sendex quality score, with official libraries for PHP, Node.js, Ruby and Python.
The table uses Kickbox's public pricing and documentation pages as checked on 2026-09-03, and Spaw's own pricing page. A row those pages carry no value for is marked "not on the pages read" rather than guessed at, and that is a statement about the reading and not about what Kickbox publishes.
| spaw | kickbox | |
|---|---|---|
| Pricing model | Pay-as-you-go credit packs whose credits never expire, or optional plans, billed monthly or yearly, that deposit the same credits every month for less and roll unused plan credits over up to three months' allowance; both through Stripe Checkout | not on the pages read |
| Free tier | 100 free credits every month, no card required | not on the pages read |
| Price per 1,000 at about 10k | $7.80 (Growth pack: 5,000 credits for $39), or $5.80 on the Growth monthly plan (5,000 credits for $29 a month) | not on the pages read |
| Price per 1,000 at about 100k | $4.49 (Volume pack: 100,000 credits for $449), or $3.49 on the Volume monthly plan (100,000 credits for $349 a month) | not on the pages read |
| Unknown or catch-all results billed | No: an unconfirmed mailbox (reason unverified) and an answer Spaw could not obtain because its handshake partner was unavailable are free and leave no 7-day repeat marker, so a later lookup is a fresh one; a catch-all answer costs 1 credit like any risky answer, and an automatic re-check bills 1 credit only when it confirms the mailbox | not on the pages read |
| Undeliverable results billed | No, within a fair use: undeliverable answers that needed a mailbox probe are free up to max(500, your billed email answers) in a rolling 30 days, then 1 credit each; the rest are always free | not on the pages read |
| SMTP mailbox check | Yes | not on the pages read |
| Catch-all handling | A catch-all answer is remembered per domain for 7 days, and every unconfirmed mailbox carries a published 0 to 100 mailbox_confidence estimate | Results are deliverable, undeliverable, risky or unknown; how accept-all domains are billed is not published on the pages we could read |
| Bulk limit | 100,000 addresses per bulk job, with an HMAC-signed completion webhook | not on the pages read |
| Batch API | 50 addresses per synchronous request, probes sent concurrently | not on the pages read |
| Rate limit | 5 requests per second per key on the email and consistency endpoints | not on the pages read |
| Official SDKs | Python, Node.js, PHP | PHP, Node.js, Ruby, Python |
| Data retention | Only email verification keeps a history row, for 30 days, then pruned; test addresses are never logged | not on the pages read |
checked 2026-09-03 · sources: Kickbox GitHub organization, Kickbox Python client README
When Kickbox fits better
Teams that want a single quality score next to the verdict and already build on one of Kickbox's four official libraries.
- Sendex score: a quality estimate between 0 (no quality) and 1 (perfect quality)
- Four official client libraries on GitHub
When Spaw fits better
Developers who want one flat price per answered lookup across every signal a signup form produces, a transparent risk score, and an API that documents every field.
- Kickbox's website blocked automated reading when we checked, so its prices are not reproduced here; Spaw's packs and free grant are listed at spaw.co/pricing
- Spaw's risk score is a 0 to 100 sum of published weights; Kickbox's Sendex score is a 0 to 1 quality estimate
- Both report deliverable, undeliverable, risky and unknown-style outcomes; Spaw adds a machine-readable reason and 46 named fields per address
- Spaw bills nothing for unverified mailboxes, for undeliverable verdicts within a fair-use allowance, or for repeats within 7 days
Questions
Does Spaw charge for catch-all or unknown results?
Spaw bills per answer, not per probe outcome. A catch-all domain comes back risky with reason catch_all and costs 1 credit like any risky answer. A mailbox the handshake could not confirm (greylisting, a timeout, no definite answer) comes back risky with reason unverified and is free, and so is an answer Spaw could not obtain at all because its handshake partner was unavailable; neither leaves a 7-day repeat marker, so a later lookup is a fresh one (an uncertain result is reused for up to 15 minutes, then the mailbox is asked again) and bills 1 credit only once the mailbox is confirmed, and the automatic re-checks behind callback_url bill 1 credit only when they confirm it. Undeliverable verdicts are free within a fair use of max(500, your billed email answers) in a rolling 30 days, and invalid input and repeats within 7 days are free too. Kickbox does not publish how it bills them.
Can I move a list from Kickbox to Spaw?
Yes. Upload the CSV to the dashboard or POST it to the bulk endpoint; Spaw keeps your columns, adds the verdict columns, and lets you download only the deliverable, risky or undeliverable rows. Addresses that come back undeliverable join your suppression list so later runs skip them for free.
Is there a free tier?
Every Spaw account receives 100 free credits at the start of each month with no card on file, and unused free credits accumulate. Kickbox does not publish a free tier on the pages checked.
Try Spaw on your own list
Free credits every month, no card. Upload a list, keep your columns, and download only the rows you want. See the pricing page for every rule, or the Kickbox alternatives.
Kickbox is a trademark of its owner. Spaw is not affiliated with it. Markdown version: /compare/kickbox.md