Kickbox sells pay-as-you-go packs: $10 for 1,000, $70 for 10,000, $500 for 100,000 and $2,999 for a million, and credits expire one year from purchase (kickbox.com, read 24 September 2026). ZapBounce charges $5 for 1,000, $25 for 10,000, $139 for 100,000 and $949 for a million, and the credits carry no date at all.
That expiry date shapes the whole move. You don't want to strand a balance you paid for, and you don't want a gap where nothing checks your signups. This guide runs both tools side by side for a short window, then turns Kickbox off. The ZapBounce vs Kickbox page covers the full comparison.
The short version
- Your Kickbox balance, its purchase dates, and your recent result exports
- A ZapBounce account (100 free checks a month, no card) with a live key and a zb_test_ sandbox key
The steps
Check when your Kickbox credits lapse
Look up the purchase date of each Kickbox pack. Credits run out one year after that date, so plan the switch for after the balance is spent, or before the oldest pack lapses.
Export your recent Kickbox results
Download the result files for every list you still mail. Keep each address's last result, its Sendex score and the check date as your record.
Write down every rule that reads Kickbox
Search your code, ESP segments and Zaps for Kickbox's result and reason values and any Sendex threshold. Note what each rule does, such as send, drop or hold.
Turn Sendex thresholds into result rules
Rewrite a rule like "send when Sendex is high" as a rule on the ZapBounce
resultand flags. Sendvalidrows. Sendcatch_allrows to a slower, warmed sequence. Dropinvalid, and hold rows wheredisposableorroleis true for review.Build against the sandbox key
Call
POST https://api.zapbounce.com/v1/verifywith a JSON body holdingemailand your key in anAuthorization: Bearerheader.zb_test_calls never bill, so your test suite runs free. The result codes docs list everyresultandreason.Move list jobs and webhooks
Upload files with
POST /v1/files, or send up to 100,000 addresses as JSON withPOST /v1/batches. Subscribe tobatch.completedand check theZapBounce-Signatureheader on each delivery.Run both for one week, then switch
Send the same signups through both tools for a week and compare the rows where they differ. When your rules behave, move the live key to
zb_live_and turn the Kickbox calls off.Re-check lists older than a month
Upload any list last checked more than a month ago to the bulk page. A result describes the mailbox on the day of the check, and business addresses change as people move jobs.
From a quality score to a verdict you can act on
Kickbox's Sendex score rates how good an address looks. ZapBounce answers one question per address, whether the mailbox exists, and reports four results: valid, invalid, catch_all and unknown. A reason field says why, and the smtp_code field shows the literal reply the server gave.
Three flags sit beside the result: role for info@ and sales@ style addresses, disposable for throwaway domains, and free_provider for consumer mail. Each flag is a yes or a no, so a segment rule is one line in your ESP rather than a score cut-off you have to tune.
What changes on your bill
ZapBounce bills one credit when a mail server gave us an answer. valid, invalid and catch_all cost a credit. An unknown, a duplicate in the same batch, a syntax reject and any error on our side cost nothing, and each row's billed field shows it.
Credits never expire. If you clean a list twice a year, a 100,000 pack at $139 lasts until you use it. All tiers are on the pricing page.
Questions people ask
How do I migrate from Kickbox to another email verifier?
Spend or log your Kickbox balance, export recent results, rewrite Sendex thresholds as rules on the new tool's results, swap the API calls, and run both for a week. ZapBounce sandbox keys never bill, so the test week costs nothing.
Do Kickbox credits expire?
Yes. Kickbox credits expire one year from purchase, per kickbox.com read on 24 September 2026. ZapBounce credits never expire, from $5 for 1,000 checks.
What replaces the Kickbox Sendex score?
At ZapBounce, rules read the result and three flags instead of a score. Send valid rows, warm catch_all rows slowly, drop invalid rows, and review role and disposable addresses.
How much does Kickbox cost for 10,000 emails?
Kickbox charges $70 for 10,000 verifications, per kickbox.com read on 24 September 2026. ZapBounce charges $25 for 10,000, and unknown results are never billed.