Email Verification Cost Calculator & Price Matrix
By Aria Pramesi, founder of InboxPolicy · Updated July 6, 2026
BLUF: InboxPolicy charges $0.005 per fresh verification from a $5 prepaid pack, with cache hits free forever — versus $0.008 per check at ZeroBounce and $0.01 at Kickbox, which bill every lookup including repeats. AI agents can also pay $0.01 per call keyless via x402 USDC on Base, no account. Use the calculator below to model your own cost.
Vendor price matrix: what email verification actually costs
Per-check list prices for the major email verification vendors (July 2026). InboxPolicy's number is the $5 Starter pack rate ($5.00 per 1,000 = $0.005/check); the keyless x402 rail is $0.01/call and lives in its own column. Competitor list prices are pulled from our InboxPolicy vs ZeroBounce and catch-all verification reference pages.
| Vendor | Price per 1,000 (list) | Per-check | Cache / repeat hits | Keyless agent pricing (x402) | Free tier |
|---|---|---|---|---|---|
| InboxPolicy | $5 (Starter pack) | $0.005 | FREE (72h cache) | $0.01/call USDC on Base | None ($5 pack is the trial) |
| ZeroBounce | ~$8.00 | $0.008 | No — full price every lookup | No | 100 / month |
| Kickbox | ~$10.00 | $0.01 | No — full price every lookup | No | One-time credits |
| MillionVerifier | ~$0.59–2.50 | ~$0.0006–0.0025 | No — full price every lookup | No | Yes |
| NeverBounce | ~$8.00 (list) | ~$0.008 | No — full price every lookup | No | Not specified |
List prices are the vendors' public entry rates; InboxPolicy's pack rate drops further at volume ($3.80/1k Builder, $3.16/1k Growth). ZeroBounce, Kickbox and MillionVerifier figures match our comparison pages; the NeverBounce figure is its published pay-as-you-go entry rate and entry pricing varies — check the vendor's current pricing before relying on it.
Feature & cost-tradeoff matrix
Price is only half the picture. These are the structural cost drivers that compound over time — repeat-lookup billing, keyless pay-per-call, a hosted MCP server for agents, and an in-house SMTP engine.
| Vendor | Send-decision verdict | Cached re-verification cost | Per-call crypto payment | Hosted MCP for agents | Self-hosted engine option |
|---|---|---|---|---|---|
| InboxPolicy | Yes | Free | Yes | Yes | Yes |
| ZeroBounce | No (status fields) | Full price | No | No | No |
| Kickbox | No (status + score) | Full price | No | No | No |
| MillionVerifier | No (status fields) | Full price | No | No | No |
| NeverBounce | No (status fields) | Full price | No | No | No |
"Self-hosted engine option" means InboxPolicy operates its own SMTP verification engine in-house rather than depending on a third-party verifier API — giving direct control over probing and marginal cost. Competitor entries are marked "No" where our reference pages do not document otherwise.
Bounce-cost worked examples
Three scenarios with the arithmetic shown inline. Example (a) uses pack pricing ($0.005/check); the x402 figure appears in (b).
(a) 10,000-email list at a 12% hard-bounce rate
Cleaning the full list once, fresh lookups only:
- InboxPolicy: 10,000 × $0.005 = $50 (re-checks of stable addresses within 72h later = $0)
- ZeroBounce: 10,000 × $0.008 = $80
- Kickbox: 10,000 × $0.01 = $100
InboxPolicy saves $30 (vs ZeroBounce) to $50 (vs Kickbox) on a single clean — before any repeat-lookup savings.
(b) AI agent making 1,000 live send-decision calls
An agent that verifies each recipient right before sending, keyless:
- InboxPolicy x402: 1,000 × $0.01 = $10 in USDC on Base, no signup, no API key, settles on-chain per call
- Incumbents: the keyless per-call path does not exist — ZeroBounce, Kickbox, MillionVerifier and NeverBounce all require an account and a prepaid balance or plan
For sustained volume, InboxPolicy's $5 pack ($0.005/check) undercuts even its own x402 rate: 1,000 calls on a pack = $5.
(c) 30%-churn list re-cleaned monthly over 12 months
Same 10,000-address list, 30% of addresses churn (turn over) each month. Stable addresses stay cached; only the new 30% re-price as fresh.
- InboxPolicy: month 1 full = 10,000 × $0.005 = $50; months 2–12 = 11 × (3,000 new × $0.005) = 11 × $15 = $165 → annual total = $215
- ZeroBounce (re-charges full price 12×): 12 × (10,000 × $0.008) = 12 × $80 = $960
- Kickbox (re-charges full price 12×): 12 × (10,000 × $0.01) = 12 × $100 = $1,200
InboxPolicy saves $745 vs ZeroBounce and $985 vs Kickbox over the year.
Caveat for (c): InboxPolicy's free cache window is 72 hours, so the "stable addresses free" line holds when your re-verification cadence keeps those addresses inside the 72h window (e.g. you re-verify more often than monthly). Outside that window they re-price as fresh. The annual figure above models the best case where stable addresses remain cached.
Cost calculator
Model your own list. Defaults reflect example (a): 10,000 addresses, 12% hard-bounce rate, InboxPolicy's $5/1k pack rate. Outputs compare against the $8/1k (ZeroBounce) and $10/1k (Kickbox) list benchmarks.
Frequently asked questions
How much does InboxPolicy cost per email verification?
InboxPolicy costs $0.01 per fresh verification via x402 (paid in USDC on Base, no account), or from a prepaid credit pack: $5 for 1,000 credits ($0.005/check), $19 for 5,000 ($3.80/1k), and $79 for 25,000 ($3.16/1k). Cache hits within 72 hours and malformed-email rejections are free.
Are repeat (cached) verifications really free?
Yes. Every fresh verification is cached for 72 hours. Re-checking the same address inside that window returns the cached result marked from_cache: true and costs 0 credits. Malformed emails are rejected before SMTP at no charge, and idempotent retries on the same key are never billed twice.
How does the $0.01 per-call x402 pricing for AI agents work?
An agent with a wallet calls POST /v1/decide with no account or API key. The API responds 402 Payment Required with machine-readable requirements; the agent pays $0.01 in USDC on Base via an X-PAYMENT header and receives the decision plus an on-chain settlement receipt. Prepaid credit packs stay cheaper ($0.005/check) for sustained volume.
How does InboxPolicy compare in price to ZeroBounce and Kickbox?
ZeroBounce's list price is about $8.00 per 1,000 ($0.008/check) and Kickbox's is about $10.00 per 1,000 ($0.01/check). InboxPolicy's Starter pack is $5 per 1,000 ($0.005/check), and every repeat within the 72-hour cache window is free — ZeroBounce and Kickbox charge full price for every lookup, including repeats.
Is there a free tier?
No. InboxPolicy has no free tier by design, because free tiers attract list-cleaning abuse that damages probe infrastructure. The $5 Starter pack (or the $0.01 x402 per-call price) functions as the trial. What is always free for customers: cache re-verification within 72 hours, malformed-email rejection, and idempotent retries.
How accurate is InboxPolicy vs MillionVerifier / ZeroBounce?
InboxPolicy's prior engine showed roughly 90% typical valid-verdict agreement with MillionVerifier across more than 2 million verifications, though it varies by vertical and can drop to around 60%. This is a directional signal, not a formal recent benchmark or a direct comparison to ZeroBounce. Unknown and catch-all results always map to review, never guessed as safe.
How are catch-all and unknown mailboxes handled?
A catch-all domain accepts mail for any address, so SMTP can't confirm the specific mailbox. InboxPolicy tags that evidence with catch_all and returns action review by default (or send_with_caution under an aggressive policy), never send. Unknown results — greylisting, a protective gateway, or catch-all — are a first-class state mapped to review, not over-promoted to safe.
Which payment methods are supported?
Two. x402 pay-per-call at $0.01 per decision in USDC on Base with no account, and Stripe card checkout for prepaid credit packs — Starter ($5), Builder ($19), Growth ($79) — with the API key emailed to you. There is no free tier; the smallest pack is the trial.
Ready to verify?
Start with a $5 Starter pack (1,000 credits, key emailed, no crypto needed) or read the API docs.
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