# CheckNumber.AI, free: Email verification API

> Check whether email addresses are active and able to receive mail. Only supports Gmail, Yandex, Mail.ru, iCloud, Outlook, and Yahoo.

CheckNumber.AI's email verification API on its Free trial plan. It costs $0.00 per 1,000 emails. It returns 1 of the 6 key fields we check: Address.
We rank 2,467 plans by price. [treg's top-up from $10](https://datacircle.dev/validate-email-apis/treg/top-up-from-10/llms.txt) costs the least per 1,000 emails: $0.00 on average. treg asks one provider after another until one answers. You pay $26.95 per 1,000 emails when no provider answers.
[Enrich.so](https://datacircle.dev/validate-email-apis/enrich-so/149-monthly/llms.txt), [GetProspect](https://datacircle.dev/validate-email-apis/getprospect/369-pack/llms.txt) and [treg](https://datacircle.dev/validate-email-apis/treg/top-up-from-10/llms.txt) are the best email verification API providers in our benchmark.

- This page: https://datacircle.dev/validate-email-apis/checknumber-ai/free
- [Best email verification API in 2026](https://datacircle.dev/best-email-verification-api.txt)
- Get it: https://checknumber.ai/pricing
- Request: `POST https://api.checknumber.ai/v1/tasks`
- API key: with the plan, on https://checknumber.ai/pricing
- Its API docs: https://docs.checknumber.ai/email-deliverability-checker/#deliverability-checker-email_check
- Sold by: CheckNumber.AI (https://checknumber.ai)
- Checked: 2026-10-28

## In the answer

- Completeness: 17%
- Address: ✓

## Price

- $ per 1,000 emails: $0.00
- Per: result
- Billing: free

## Aggregators

- Aggregators: none

## Not found

- $ per 1,000: $0.00

## In their words

- Their pitch: Check whether email addresses are active and able to receive mail. Only supports Gmail, Yandex, Mail.ru, iCloud, Outlook, and Yahoo.

## Data

- What it checks: mailbox
- Keep data: no limit
- Use data: "This license is granted solely for Your internal business purposes" (3.1), "You agree not to (a) license, sublicense, sell, resell, transfer, assign, distribute, or otherwise commercially exploit or make available to any third party the Service in any way, except as expressly permitted by these Terms or an Agreement, (b) modify or make derivative works based upon the Service, (c) reverse engineer, decompile, or disassemble the Service or attempt to gain unauthorized access to the Service or its related systems or networks, or (d) use the Service for any purpose or in any manner that is unlawful (including in violation of the PDPA) or prohibited by these Terms. Furthermore, You agree that any phone numbers or associated data obtained through the Service shall not be used by You or any third party acting on Your behalf to: (i) contact any individual without their prior, express, and informed consent for such contact, in accordance with PDPA requirements, (ii) send unsolicited commercial communications (spam), bulk messages, or any messages in violation of applicable anti-spam laws (including the Singapore Spam Control Act) and the PDPA, (iii) send harassing, abusive, threatening, defamatory, obscene, or otherwise unlawful communications, or (iv) engage in any other practices that violate the privacy or data protection rights of individuals or any applicable laws or regulations, including the PDPA" (3.2)

## Plan

- Pay: $0
- You get: 1,000 results
- Enough for: 1,000 results, once

## Rate limit

- Batch: 1,000,000

## Speed

- Answer: by polling

## The call

- You send: file, task_type "email_check"
- Method: POST
- Path: /v1/tasks

## About the plan

- Plan: Free trial
- Who can get it: anyone who contacts support

## The 2 fields the plan's answer can hold

email address, activated

## CheckNumber.AI's plans (3)

- [CheckNumber.AI, free](https://datacircle.dev/validate-email-apis/checknumber-ai/free/llms.txt): $0.00 per 1,000, 17% complete
- [CheckNumber.AI, top-up from $20](https://datacircle.dev/validate-email-apis/checknumber-ai/top-up-from-20/llms.txt): $0.50 per 1,000, 17% complete
- [CheckNumber.AI, contact us](https://datacircle.dev/validate-email-apis/checknumber-ai/contact-us/llms.txt): 17% complete

## CheckNumber.AI's calls for this API (1)

- `POST /v1/tasks`: [CheckNumber.AI, free](https://datacircle.dev/validate-email-apis/checknumber-ai/free/llms.txt)

## CheckNumber.AI's APIs (2)

- [CheckNumber.AI: email verification API pricing, 3 plans](https://datacircle.dev/validate-email-apis/checknumber-ai/free/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, Band Checker](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-band-checker/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/phone](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-phone/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, iMessage Checker](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-imessage-checker/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, Line Checker](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-line-checker/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, Line Profile Checker](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-line-profile-checker/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, MAX Checker](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-max-checker/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, MAX Full Profile Checker](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-max-full-profile-checker/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, Messenger Checker](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-messenger-checker/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, Number Activity](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-number-activity/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, Number Validation](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-number-validation/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, Phone Carrier Bulk Lookup](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-phone-carrier-bulk-lookup/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, RCS Checker](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-rcs-checker/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, Signal Checker](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-signal-checker/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, Telegram Age & Gender Checker](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-telegram-age-gender-checker/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, Telegram Checker](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-telegram-checker/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, Telegram Number Activity](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-telegram-number-activity/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, US Carrier Advanced](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-us-carrier-advanced/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, Viber Age & Gender Checker](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-viber-age-gender-checker/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, Viber Checker](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-viber-checker/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, Viber Number Activity](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-viber-number-activity/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, WhatsApp Advanced](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-whatsapp-advanced/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, WhatsApp Age & Gender Checker](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-whatsapp-age-gender-checker/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, WhatsApp Checker](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-whatsapp-checker/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, WhatsApp Number Activity](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-whatsapp-number-activity/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, Zalo Age & Gender Checker](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-zalo-age-gender-checker/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, Zalo Checker](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-zalo-checker/llms.txt)
- [CheckNumber.AI: phone validation API pricing, 3 plans, POST /v1/tasks, Zalo Number Activity](https://datacircle.dev/validate-phone-apis/checknumber-ai/free-trial-post-v1-tasks-zalo-number-activity/llms.txt)

## CheckNumber.AI: email verification API alternatives

- [Sealch, $25 monthly, Monthly up to 50,000 / mo, POST /api/verify](https://datacircle.dev/validate-email-apis/sealch/25-monthly-monthly-up-to-50000-mo-post-api-verify/llms.txt): $0.50 per 1,000, 17% complete, live
- [Verimail, $500 pack](https://datacircle.dev/validate-email-apis/verimail/500-pack/llms.txt): $0.50 per 1,000, 50% complete, live
- [Mailerio, $500 monthly, Monthly 1,000,000 emails, GET /v{version}/validate](https://datacircle.dev/validate-email-apis/mailerio/500-monthly-monthly-1000000-emails-get-v-version-validate/llms.txt): $0.50 per 1,000, 67% complete, live
- [NullBounce, $500 pack](https://datacircle.dev/validate-email-apis/nullbounce/500-pack/llms.txt): $0.50 per 1,000, 33% complete, live

## Sources

From each provider's own pricing page and docs, and from what providers tell us. We read this row from these pages on 2026-10-28.

- https://checknumber.ai/llms.txt
- https://checknumber.ai/pricing
- https://checknumber.ai/terms
- https://docs.checknumber.ai
- https://docs.checknumber.ai/email-deliverability-checker/