Key takeaways
- check_circleEvery API on this page runs a real SMTP handshake. The differences are in price, in how a catch-all comes back, and in how much you can push through per minute. Read the JSON before you read the marketing.
- check_circleAt the entry tier, cost per 1,000 checks varies by more than 140x. Mailsfinder works out around $0.13 per 1,000 on the $9.99 Starter plan, Reoon around $1.19 on its smallest credit pack, and ZeroBounce around $19.50 at 2,000 pay-as-you-go credits.
- check_circleKickbox, Emailable and Clearout sit in the middle at roughly $5 to $10 per 1,000 at entry, dropping to $1 to $4 per 1,000 above 100,000 checks.
- check_circleOnly two vendors here also find addresses through the same key: Mailsfinder at 3 credits per found address and Hunter through its separate finder credits. Everyone else verifies what you already have.
- check_circleFree tiers range from 100 one-time checks (Kickbox, Bouncer, Clearout) to 100 a day forever (Mailsfinder) and 600 a month (Reoon). A daily allowance is the one you can build a test suite against.
- check_circleCatch-all handling is where the answers diverge. ZeroBounce sells a separate scoring product for them, Bouncer and Clearout return a distinct status, Mailsfinder returns Unknown in the API and risky in the app. None of them can confirm a mailbox on a catch-all domain, whatever the status is called.
- check_circleRate limits are rarely published. Mailsfinder states 600 requests a minute on paid plans. Most others describe limits as plan dependent, so budget a 429 handler with backoff regardless of vendor.
- check_circleNeverBounce is not on this page. Its pricing page refuses automated access, and we do not print prices we could not read ourselves.
What an email verification API does, and what it cannot
An email verification API takes an address and tells you whether a mailbox exists at the other end, without sending anything. The good ones do it in four steps: check the syntax, look up the domain's MX records, open an SMTP conversation with the mail server and ask whether the mailbox is there, then translate the server's answer into a status you can act on. The whole thing takes between a few hundred milliseconds and a couple of seconds, depending on how quickly the receiving server responds.
Where the APIs differ is in what they do with ambiguity. A catch-all domain accepts every address, so the SMTP check cannot confirm a specific mailbox. A greylisting server refuses the first attempt on purpose. A mail server can simply time out. Each vendor names these cases differently, and some sell an extra product to guess at them. Read the status list in the documentation before you integrate, because that list is what your code will branch on.
The other difference is price, and it is larger than most buyers expect. At the entry tier the spread on this page runs from roughly $0.13 to roughly $19.50 per 1,000 checks. At volume it narrows, but a nightly job that re-verifies a 200,000 address list costs a very different amount at each end of that spread, and that is the number to put in the spreadsheet rather than the headline plan price.
One thing no API here can do is promise the inbox. Verification removes the addresses that would bounce. It does nothing about your sending reputation, your authentication records or your content. It is the cheapest step in deliverability and the one to do first, and that is all it is.
The tools at a glance
How we evaluated these tools
Every price below came from the vendor's own pricing page or from our research data verified against it in September 2026. Where a vendor publishes a rate limit, we quote it; where they do not, the table says so instead of inventing one. NeverBounce was dropped after its pricing page refused automated access three times, because a listicle that prints prices it could not read is worth less than one with seven vendors.
Cost per 1,000 at two tiers
The entry rate and the rate at 100,000 checks, because most teams start small and the gap between the two tells you how the bill scales.
What the JSON returns
Which statuses exist, how a catch-all is reported, and whether the response carries the MX host and a reason. A verifier that returns only valid or invalid hides the cases that matter.
Rate limits and batch endpoints
Whether the vendor publishes requests per minute, and whether there is a bulk endpoint so a list does not have to be sent one address at a time.
Free tier you can build against
One-time credits let you try the API. A recurring allowance lets you run a test suite every day without a card, and only two vendors here offer that.
Three kinds of verification API, and which you are buying
The vendors do not label themselves this way, but the pricing pages do, and the split explains most of the cost difference.
Verify-only APIs
Take an address, return a status. Nothing else. Kickbox, Emailable, Reoon, Bouncer are the cleanest examples. Simple to integrate, and priced purely per check.
Verify plus deliverability suite
ZeroBounce and Clearout wrap verification in scoring, inbox testing, blocklist monitoring and integrations. Useful if you want one vendor, and you pay for the breadth on every check.
Verify plus find
Mailsfinder and Hunter sell the finder and the verifier through one key. If your pipeline starts with names rather than addresses, this is the type that saves a second integration.
Every tool, side by side
Rank is a table position, not a promotional order.
| Tool | Type | Entry price | Cost per 1,000 at entry | Free tier | Rating |
|---|---|---|---|---|---|
| Mailsfinder | Verify plus find | $9.99/mo | ~$0.133 | 100 credits a day | New on G2 |
| ZeroBounce | Verify plus suite | $39 for 2,000 credits | ~$19.50 | 100 a month | 4.7/5 (1,361) |
| Emailable | Verify-only | $38 for 5,000 credits | ~$7.60 | 250 once | New on G2 |
| Kickbox | Verify-only | $5 for 500 verifications | ~$10.00 | 100 once | New on G2 |
| Bouncer | Verify-only | $8 for 1,000 credits | ~$8.00 | 100 once | New on G2 |
| Clearout | Verify plus suite | $19.50/mo for 3,000 credits | ~$5.33 | 100 lifetime | New on G2 |
| Reoon | Verify-only | $11.90 for 10,000 credits | ~$1.19 | 600 a month | 4.8/5 (1,018) |
| Hunter | Verify plus find | $11 for 1,000 verification credits | ~$11.00 | 50 a month | 4.4/5 (634) |
Pricing read from each vendor's pricing page or verified research data, September 2026. Ratings shown only where our research data carries a verified figure and review count, because G2 blocks automated access. Cost per unit uses each vendor's best published rate, which is usually a larger pack or plan than the entry price in the column beside it, so the two do not divide into each other.
Cost calculator
What a verification job costs, API to API
Figures use each vendor's published rate at the tier the volume falls into, so a 1,000,000 check job is priced on the 1,000,000 pack rather than the entry rate. Mailsfinder is priced on the Starter plan, 75,000 credits for $9.99, with additional months added when the job exceeds it.
| Tool | Checks you get | Rate used |
|---|
Rates read from each vendor's pricing page or verified research data, September 2026. Mailsfinder priced on the Starter plan; vendors with never-expiring packs priced on the pack that covers the volume.
The tools, reviewed
Every tool gets the same card: what it is, four features, three pros, three cons, and an honest read. Same format for ours as for everyone else's.
Mailsfinder
Verify and find, one key
This is our API, so check every number here against the pricing page and read the cons first. Four endpoints share one Bearer key: verify one address, verify a list, find one address from a name and domain, find a list. A verification is one credit and returns email, status, domain and processing time; a find is 3 credits and only when an address comes back. The $9.99 monthly plan carries 75,000 credits, which is where the $0.13 per 1,000 figure comes from, and the 600 requests a minute limit is printed on the pricing page rather than hidden in a support article.
Key features
- checkverifyEmail and verifyBulkEmail return Valid, Invalid or Unknown with the domain and timing in one JSON object.
- checkfindEmail in the same key takes first name, last name and domain and returns a verified address at 3 credits, or nothing at no charge.
- checkPublished rate limit 600 requests a minute on Starter and Annual, 300 on Lifetime, with 429 and backoff documented.
- checkDaily free allowance 100 credits every day with API access, so a test suite runs without a card.
Pros
- addLowest cost per 1,000 checks on this page
- addFinder and verifier behind one key
- addDaily free credits with API access
Cons
- removeCatch-all comes back as Unknown, no score
- removeNo official SDKs, REST and examples only
- removeNewer platform with a thin review record
The honest read
The price is the argument and it is a large one. What you give up is the scoring and monitoring layers ZeroBounce and Clearout sell, and a client library in your language. If you need a number attached to a catch-all rather than an Unknown, look at the next two entries.
ZeroBounce
Verification with a deliverability suite
With 1,361 reviews on G2 and a 4.7 rating, ZeroBounce has the longest track record of any vendor on this page, and its API reflects that: a rich status list, an activity data add-on, a separate AI scoring product for addresses the handshake cannot settle, and integrations into most ESPs. The cost of all that is the highest entry rate here, around $19.50 per 1,000 at 2,000 pay-as-you-go credits, falling on the ZeroBounce ONE subscription to roughly $7.90 per 1,000 at 10,000 credits a month on annual billing. Email finding is a separate product at 20 credits per successful search.
Key features
- checkValidation API with detailed sub-statuses including catch-all, role-based, disposable, toxic and abuse flags in one response.
- checkAI scoring for catch-all addresses as a separate product, returning a deliverability score where the SMTP check cannot confirm.
- checkBulk file API uploads a list and returns a downloadable result file when processing completes.
- checkZeroBounce ONE bundle adds inbox tests, warmup seeds, blocklist monitors and finder credits on one subscription.
Pros
- addDeepest status list of any API here
- addLargest verified review base, 1,361 on G2
- addScoring and monitoring in the same account
Cons
- removeHighest entry rate at around $19.50 per 1,000
- removeScoring is a separate paid product
- removeFinder is 20 credits per search, separate
The honest read
The right choice when you want one vendor for verification, monitoring and inbox testing and the per-check price is not the deciding factor. For a pure verification job at volume, it is the most expensive line in the calculator by a wide margin.
Emailable
Verify-only, scored responses
Developer-facing from the first screen, Emailable publishes its API reference next to its pricing and returns a numeric score alongside the state, which helps when you have to make a call on an accept-all domain. Pay-as-you-go starts at $38 for 5,000 credits, around $7.60 per 1,000, and a monthly subscription takes 15 percent off that. At 100,000 credits the pay-as-you-go rate is $420, or $4.20 per 1,000, and it reaches $2.10 per 1,000 at a million. Credits never expire and unused subscription credits roll over, which is rarer than it should be.
Key features
- checkScore with every result a 0 to 100 number next to the state, useful for accept-all decisions.
- checkBatch API sends a list and polls for a result, so large jobs are one request.
- checkCredits never expire and subscription credits roll over month to month.
- check15 percent subscription discount for teams with a steady monthly volume.
Pros
- addScore attached to every response
- addCredits never expire, subscription credits roll over
- addClear public API documentation
Cons
- removeEntry rate around $7.60 per 1,000
- removeFree tier is 250 once, not recurring
- removeNo finder, verification only
The honest read
A clean verify-only API with a scoring model that helps on the hard cases, priced in the middle of the pack. It becomes competitive above 100,000 checks; at entry, Reoon and Mailsfinder are far cheaper for the same handshake.
Kickbox
Verify-only, flat pricing
Kickbox does one thing and prices it on a single page you can read in ten seconds: $0.01 per verification up to 2,500, $0.008 from 5,000 to 100,000, then $0.006, $0.005 and $0.004 at 250,000, 500,000 and a million. No subscription, no minimum, credits valid for a year. The API mirrors that simplicity, with a single-address endpoint and a batch endpoint that returns a result file. It is the vendor to pick when you want the integration finished this afternoon and the bill to be predictable.
Key features
- checkFlat per-check pricing published as a table, $0.01 down to $0.004 per verification by pack size.
- checkBatch verification API uploads a file and returns a download URL when it completes.
- checkSendex score a quality score returned with each result to rank deliverable addresses.
- checkNo subscription credits are bought in packs and last a year.
Pros
- addPricing fits on one line
- addNo subscription or minimum commitment
- addBatch endpoint with a downloadable result
Cons
- removeAround $10 per 1,000 at the smallest pack
- removeFree tier is 100 once
- removeVerification only, no finder
The honest read
The most predictable bill on this page and the fastest to integrate. It is also the second most expensive at entry, so it suits a signup form doing thousands of checks a month more than a nightly list job doing hundreds of thousands.
Bouncer
Verify-only with a toxicity check
Read live on 22 September 2026, Bouncer's credits run from $8 for 1,000 to $2,000 for a million, which is $0.008 per check at entry and $0.002 at the top, with 5,000, 10,000, 50,000 and 100,000 packs in between. The API returns a distinct catch-all status rather than folding it into unknown, and adds a toxicity check that flags addresses seen in breaches or spam traps. A separate deliverability product sells inbox placement tests by the month, which is not the same thing and is priced per test email rather than per verification.
Key features
- checkDistinct catch-all and role statuses so your code can branch on them instead of on a generic unknown.
- checkToxicity check flags addresses linked to breaches, complaints and spam traps.
- checkBatch API with real-time or bulk modes for single addresses at capture and lists overnight.
- checkVolume pricing to $0.002 at a million credits, one of the lower ceilings here.
Pros
- addCatch-all returned as its own status
- addToxicity data included in the check
- addDrops to $0.002 per check at volume
Cons
- removeAround $8 per 1,000 at the smallest pack
- removeFree tier is 100 once
- removeInbox testing is a separate monthly product
The honest read
A well-designed verify-only API whose status list is more useful than most. Entry pricing is middle of the pack, and the deliverability add-on is a separate bill, so treat it as a verifier and price it as one.
Clearout
Verify plus finder and integrations
Clearout prices by subscription rather than by pack: Starter is $19.50 a month for 3,000 credits, or $16 a month on annual billing, which is where the $0.0053 per check figure comes from. Pro tiers run from 10,000 credits at $58 a month up to a million at $800 a month on annual billing, or $0.0008 per check. Credits roll over and never expire. The API covers verification, an email finder and a set of CRM and ESP integrations, and the free tier is 100 credits for the life of the account rather than a monthly refill.
Key features
- checkSubscription credits that roll over so unused volume is not lost at month end.
- checkVerification API with catch-all handling returning a distinct status for accept-all domains.
- checkEmail finder and prospecting endpoints in the same account, priced separately from verification.
- checkAnnual billing at 20 percent off which is the rate quoted in the cost per 1,000 column.
Pros
- addCredits roll over and never expire
- addVerification, finder and integrations in one account
- addAround $0.80 per 1,000 at a million credits
Cons
- removeMonthly rate is $19.50 for 3,000, higher than annual
- removeFree tier is 100 for the lifetime of the account
- removePricing page is dense with tiers
The honest read
Good value on annual billing and one of the few subscription models here that does not punish an uneven month. On monthly billing the entry rate is closer to $7.70 per 1,000, so read the annual and monthly columns separately.
Reoon
Verify-only, lowest pack price
The cheapest pay-as-you-go pack on this page is Reoon's: 10,000 credits for $11.90, around $1.19 per 1,000, never expiring, with a million credits at $960. A daily-credit subscription starts at $9 a month for 500 a day, and the free tier refills to 600 a month, which is enough to develop against. The API offers a quick mode that skips the SMTP step for speed and a power mode that runs the full handshake, and 1,018 reviews on G2 at 4.8 put it second only to ZeroBounce in verified feedback here.
Key features
- checkQuick and power verification modes one for speed at capture, one for the full SMTP check in bulk.
- checkCredits that never expire on the instant packs, from 10,000 at $11.90.
- checkDaily-credit subscriptions from $9 a month for 500 a day, for steady small volumes.
- checkRecurring free tier 600 credits a month, refilled daily on login.
Pros
- addAround $1.19 per 1,000 at the smallest pack
- addFree tier refills to 600 a month
- add1,018 G2 reviews at 4.8
Cons
- removeQuick mode skips the SMTP step, read the docs
- removeVerification only, no finder
- removeDaily plans cap throughput per day
The honest read
The best pure verifier value after Mailsfinder and a stronger review record than most. Make sure your integration calls power mode where accuracy matters, because quick mode is a different check.
Hunter
Finder-first, verification credits separate
Hunter is the finder most developers already know, and its verification API is sold alongside it rather than as the headline. Bulk verification credits on the data platform run $11 per 1,000, $110 for 10,000, $690 for 150,000 and $2,800 for a million, which is $0.011 falling to $0.0028 per check. The finder itself is on the subscription, from $49 a month for 2,000 searches. With 634 G2 reviews at 4.4 it has the broadest name recognition here, and the API is documented to the standard that reputation implies.
Key features
- checkEmail Verifier endpoint returns a status, a score and the sources where Hunter has seen the address.
- checkFinder and Domain Search in the same key for pipelines that start with a name or a company.
- checkBulk verification credits sold separately from the subscription, from $11 per 1,000.
- checkWell-known API surface with SDKs and community libraries in most languages.
Pros
- addFinder, domain search and verifier under one key
- addClient libraries in most languages
- add634 G2 reviews at 4.4
Cons
- removeAround $11 per 1,000 verifications at entry
- removeFinder needs the $49 a month subscription
- removeFree tier is 50 credits a month
The honest read
If you are already a Hunter customer, adding verification is one line. If you are not, buying Hunter for verification alone is paying finder prices for a verifier, and Mailsfinder or Reoon do the same handshake for a fraction of the cost.
Which one fits your situation
Pick the row that matches the job in your backlog, not the vendor with the longest status list.
| If this is you | Start here |
|---|---|
| You are adding verification to a signup form | You need a fast single-address endpoint and a free tier that covers your test suite. Mailsfinder gives 100 checks a day without a card, Reoon 600 a month. Both return within a second or two on most domains. |
| You re-verify a large list every night | Cost per 1,000 at volume is the only number that matters. Mailsfinder at around $0.13 per 1,000 and Reoon at around $1 per 1,000 are an order of magnitude below the rest; use the batch endpoint so the job is one request, not 200,000. |
| Your pipeline starts with a name and a company | You want a finder and a verifier behind one key. Mailsfinder charges 3 credits per found address and nothing for a miss; Hunter sells finder credits separately from verification credits. |
| You want scoring for catch-all domains | ZeroBounce sells an AI score for addresses the handshake cannot confirm, and Emailable returns a per-address score. Treat any score on a catch-all as a guess with a confidence attached, which is what it is. |
| You want one vendor for verification, blocklist monitoring and inbox tests | ZeroBounce and Clearout bundle those, and you pay a higher per-check rate for the convenience. Fine if you would buy the extras anyway. |
| You are on a pay-as-you-go budget with no monthly fee | Kickbox, Bouncer and Emailable all sell credit packs with no subscription, at roughly $8 to $10 per 1,000 for the smallest pack. |
Five ways verification API integrations go wrong
None of these are vendor bugs. All of them show up in the first month of a new integration.
Treating Unknown as Invalid
Unknown means the server did not give a usable answer: a catch-all, a greylist, a timeout. Suppressing every Unknown throws away real customers on catch-all domains, which includes a lot of companies on Google Workspace. Route Unknown to a retry or a human, not to the suppression list.
Verifying one address at a time when a batch endpoint exists
A 100,000 address list is 100,000 requests at 600 a minute, which is nearly three hours and a lot of 429s. Every vendor here has a bulk endpoint. Use it, and poll for the result.
Ignoring the 429
Rate limits are rarely published and often plan dependent. Write the backoff handler before the first production run, because the first production run is when you find the limit.
Integrating against a one-time free tier
100 free credits are gone before the test suite passes twice. Pick a vendor with a recurring allowance for development, or budget the smallest pack as a development cost.
Reading the plan price instead of the per-1,000 rate
$9.99 a month and $16 for 2,000 credits sound close. One is 75,000 checks and the other is 2,000. Convert everything to cost per 1,000 before comparing anything.
Category picks
Lowest cost per check
Mailsfinder works out around $0.13 per 1,000 on the $9.99 Starter plan, and the same key finds addresses at 3 credits each.
Cheapest pay-as-you-go pack
Reoon sells 10,000 credits for $11.90 that never expire, and the free tier refills to 600 a month.
Verification with a deliverability suite
ZeroBounce adds scoring, blocklist monitoring and inbox tests around the core check, with 1,361 reviews on G2 behind it.
Simplest developer experience
Kickbox keeps to one job, publishes flat $0.01 to $0.008 per check pricing, and sells credits with no subscription.
Finder and verifier through one key
Hunter pairs the best-known finder API with bulk verification credits from $11 per 1,000, if you already live in Hunter.
Subscription with rollover credits
Clearout starts at $19.50 a month for 3,000 credits that roll over, with annual billing pulling the rate down to $0.00533 per check.
What you actually pay
The same eight vendors, priced per 1,000 checks at their entry tier and at roughly 100,000 checks. The entry column is what you pay while integrating; the volume column is what a nightly re-verification job actually costs.
| Tool | Free plan | Entry price | What the entry price buys | Cost per 1,000, best plan |
|---|---|---|---|---|
| Mailsfinder | 100 credits a day, no API | $9.99/mo | 75,000 credits per cycle | ~$0.133 |
| ZeroBounce | 100 validations a month | $39 / 2,000 credits | 2,000 credits, pay as you go | ~$19.50 |
| Emailable | 250 credits on signup | $38 / 5,000 credits | 5,000 credits, pay as you go; $32.30/mo on subscription | ~$7.60 |
| Kickbox | 100 verifications on signup | $5 / 500 verifications | 500 verifications, pay as you go | ~$10.00 |
| Bouncer | 100 credits on signup | $8 / 1,000 credits | 1,000 credits, pay as you go | ~$8.00 |
| Clearout | 100 credits, lifetime | $19.50/mo (Starter) | 3,000 credits a month, roll over | ~$5.33 |
| Reoon | 600 credits a month, refills daily | $11.90 / 10,000 credits | 10,000 instant credits, never expire | ~$1.19 |
| Hunter | 50 credits a month | $11 / 1,000 verification credits | 1,000 bulk verification credits; finder from $49/mo | ~$11.00 |