Best Email Validation API in 2026: 4 APIs Compared

Q: Which email validation API detects catch-all domains?

All four. ZeroBounce returns a catch-all status, NeverBounce a catchall result and Kickbox an accept_all flag on every check. emailvalidation.io fills its catch_all field when you send catch_all=1, on paid plans from Small; known catch-all domains also come back as deliverable with the reason low_deliverability.

Email validation API response and what to compare: checks, price per email, free tier, response fields

The best email validation API depends on your volume and on what your code does with the answer. This page compares four APIs developers use for sign-up forms, CRM imports and list cleaning: emailvalidation.io, ZeroBounce, NeverBounce and Kickbox. It covers price per email, free tiers, what each response contains and how each API handles lists.

Disclosure: we make emailvalidation.io, so we are not neutral. Competitor prices and features are taken from each provider’s own pricing page and API documentation, checked October 9, 2026 (Kickbox and NeverBounce prices again on October 11, 2026); check them before you buy. For a broader comparison of ten tools, including dashboards and list uploads, see the best email verification tools.

Email validation API prices compared

API	Free	Entry price	5,000	10,000	100,000
emailvalidation.io	100 / month	$9.99 / month for 5,000	$9.99 / month	$34.99 / month (25,000)	$94.99 / month
ZeroBounce	100 / month	$39 for 2,000 credits	$69	$129	$649
NeverBounce	Free test credits	$8 for 1,000 credits	$40	$50	$400
Kickbox	100 at sign-up	$5 for 500	$40	$70	$500

Price per email: emailvalidation.io $0.002 (Small) to under $0.001 (Large); ZeroBounce about $0.02 at the smallest pack, $0.0065 at 100,000; NeverBounce $0.008 up to 5,000, $0.005 from 10,000, $0.004 from 100,000; Kickbox $0.008 at 5,000, $0.005 at 100,000. NeverBounce credits expire 12 months after purchase. ZeroBounce also sells a subscription from $99 a month for 10,000 credits, NeverBounce a Growth plan from $49 a month. All emailvalidation.io plans, including yearly billing, are on the pricing page.

What the APIs return

Field	emailvalidation.io	ZeroBounce	NeverBounce	Kickbox
Verdict	`state`: deliverable, undeliverable, unknown, plus one of 11 reasons	`status`: valid, invalid, catch-all, unknown, spamtrap, abuse, `do_not_mail`, with sub-statuses	`result`: valid, invalid, disposable, catchall, unknown, plus flags	`result`: deliverable, undeliverable, risky, unknown, plus a reason
Catch-all	`catch_all` with `catch_all=1` (Small plan and up); known catch-all domains get the reason `low_deliverability`	Own status	Own result	`accept_all` flag
Score	`score` 0–1	Separate AI scoring (1 credit)	Scoring on the Growth plan	Sendex score 0–1
Typo suggestion	`did_you_mean`	`did_you_mean`	Typos fixed automatically	`did_you_mean`
Lists	`POST /v1/bulk`, up to 100,000 per job, signed webhook	File API (send, status, get, delete)	Jobs API with callbacks	Batch API, up to 1 million per request, optional callback; list upload
Client libraries	JavaScript, Python, PHP SDKs; Ruby, Go, C#, R, Rust, Perl clients; MCP server	API wrappers	PHP, Ruby, Node.js, Python, Go, .NET, Java; JavaScript widget	PHP, Node.js, Ruby, Python libraries on GitHub
Unknown results	Not charged, within a fair-use allowance	Not charged	–	Refunded

What they check

All four check syntax, DNS/MX and the mailbox over SMTP, and flag disposable and role addresses and catch-all domains (emailvalidation.io on request, with catch_all=1 on paid plans from Small). The differences are in the extras. ZeroBounce adds spam trap detection, activity data and AI scoring, and documents a separate EU endpoint. NeverBounce corrects typos and adds the company name. Kickbox returns its Sendex quality score and refunds unknown results. emailvalidation.io returns a quality score with every request and a typo suggestion when a domain looks mistyped, counts only definitive results (deliverable or undeliverable) against your quota, and validates uploaded lists through the same API. Request and response examples are on the email validation API page; catch-all email explains what to do with addresses on catch-all domains. How each of these checks works is explained in our guide to email verification.

How to choose the best email validation API

Steady monthly volume (sign-up forms, CRM sync): a subscription is cheapest. emailvalidation.io’s plans cost a fraction of pay-as-you-go credits.
One big list once a year: pay-as-you-go credits avoid a subscription. Kickbox lists 100,000 checks for $500, NeverBounce for $400; NeverBounce’s credits expire after 12 months. One month of emailvalidation.io’s Large plan covers 100,000 checks for $94.99, and you can cancel afterwards.
Extra data about contacts: ZeroBounce’s activity data and scoring.
Many no-code connections: NeverBounce lists more than 80 integrations.
Coming from one of these vendors: our ZeroBounce alternatives, NeverBounce alternatives and Kickbox alternatives pages map their result codes to ours.

Try the result quality first: validate a sample of your own addresses with the free bulk email verifier, or call the API from your code using our guide to validate email in JavaScript.

Sources

All checked October 9, 2026:

ZeroBounce: pricing, ZeroBounce API documentation
NeverBounce: pricing (checked again October 11, 2026), NeverBounce API reference
Kickbox: pricing (checked again October 11, 2026), Kickbox API library documentation, Kickbox batch verification API
emailvalidation.io: pricing, API documentation

Frequently asked questions

What is the best email validation API?

For steady volume from your own code, emailvalidation.io costs the least per email ($9.99 for 5,000 a month, $94.99 for 100,000) and returns 21 fields per address. ZeroBounce is the pick if you want activity data or an EU endpoint, NeverBounce for its client libraries and integrations, Kickbox for a simple pay-as-you-go price list.

What is the cheapest email validation API?

For regular monthly volume, subscription plans are cheapest: emailvalidation.io costs $9.99 for 5,000 validations a month (about $0.002 per email). Pay-as-you-go credits at ZeroBounce, NeverBounce and Kickbox cost roughly $0.004–$0.02 per email depending on volume.

Is there a free email validation API?

emailvalidation.io and ZeroBounce both include 100 free validations per month (ZeroBounce with a business-domain sign-up). Kickbox lists 100 free verifications, and NeverBounce offers free test credits.

Which email validation API detects catch-all domains?

All four. ZeroBounce returns a catch-all status, NeverBounce a catchall result and Kickbox an accept_all flag on every check. emailvalidation.io fills its catch_all field when you send catch_all=1, on paid plans from Small; known catch-all domains also come back as deliverable with the reason low_deliverability.

Validate emails in your app

emailvalidation.io checks syntax, MX records and the mailbox over SMTP, flags disposable, role and free addresses and returns a quality score, in one request.

100 free validations every month. No credit card required.

{ "email": "support@emailvalidation.io", "user": "support", "tag": "", "domain": "emailvalidation.io", "format_valid": true, "mx_found": true, "smtp_check": true, "catch_all": null, "role": true, "disposable": false, "free": false, "score": 0.64, "state": "deliverable", "reason": "low_quality", "did_you_mean": "", "catch_all_resolution": null, "bounce_probability": null, "status": "valid", "sub_status": "role_based", "explanation": "The mailbox exists, but it is a role address (such as info@ or support@), usually read by a team rather than one person.", "recommended_action": "send_with_caution" }

Best email validation APIs in 2026