# FirstSales, free: Email verification API

> Check email addresses, DNS records and cold email copy from your own code, with no key.

FirstSales's email verification API on its "Public, no key" plan. It costs $0.00 per 1,000 emails. It returns 2 of the 6 key fields we check: Deliverability, Company.
You get up to 864,000 calls a month.
Half of the 2,467 plans we rank by price cost $2.00 per 1,000 emails or less. This plan and 7 others tie for the lowest price per 1,000 emails of the 2,467 plans.
[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/firstsales/free
- [Best email verification API in 2026](https://datacircle.dev/best-email-verification-api.txt)
- Get it: https://firstsales.io/developers/
- Request: `POST https://firstsales.io/api/v1/email/validate`
- API key: not needed
- Its API docs: https://firstsales.io/developers/
- Sold by: FirstSales (https://firstsales.io)
- Checked: 2026-10-23

## In the answer

- Completeness: 33%
- Deliverability: ✓
- Company: ✓

## Score

- Overall score: 0.0. We give it 0 overall because its Data score is 0.
- Price score: 100
- Data score: 0
- Cost to get started score: 100
- Bundle score: 95
- Performance score: 0. We could not measure how fast this provider answers a call, so we count it as 0.

## Price

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

## Aggregators

- Aggregators: none

## Charges

- Also pays for: Score an email domain for disposable/temporary-mailbox risk · Detect whether a domain accepts mail to any mailbox (catch-all) · Run one specific DNS/email-authentication/security check against a domain · Look up and validate a domain's DKIM record · Run SPF, DKIM, DMARC, and MX checks together with a confidence score · Reverse-DNS (PTR) lookup for an IPv4 address, with forward-confirmation · Get a domain's registration age and expiration via RDAP · Fetch every DNS record type for a domain in one call · Discover subdomains via Certificate Transparency logs · Score email content for spam-trigger risk · Score and improve a cold-email subject line · Grade a full cold-email draft across 8 deliverability/effectiveness dimensions · Score and improve a cold-email body · Detect and score personalization signals in cold-email content · Create a temporary test inbox · Read the received emails for a test inbox · List public tutorials · Get one tutorial by slug · Service health check

## Not found

- $ per 1,000: $0.00

## In their words

- Their pitch: Check email addresses, DNS records and cold email copy from your own code, with no key.

## Data

- Freshness: stored
- Keep data: no limit
- Use data: You agree to use the Service only for lawful B2B commercial outreach, and to follow all laws and regulations that apply. You must not do any of the following: [...] Resell, sublicense or white-label the Service, or make it available to anyone else, without written permission from FirstSales first. [...] Use automated scripts, bots or other tools to put artificial load on, overload or interfere with the Service's systems or the systems of mailbox providers. [...] Get around or turn off any rate limits, sending caps or security controls built into the Service.

## Plan

- Pay: $0
- Enough for: 864,000 calls a month

## Rate limit

- Per second: 0.33
- Batch: 1

## Speed

- Answer: in the call

## The call

- You send: email
- Method: POST
- Path: /api/v1/email/validate

## About the plan

- Plan: Public, no key
- Who can get it: anyone at least 18 years old, for B2B commercial use only

## The 11 fields the plan's answer can hold

valid, domain, domain exists, has MX record, reserved domain, disposable, free provider, MX records, MX priority, error, message

## FirstSales's plans (1)

- [FirstSales, free](https://datacircle.dev/validate-email-apis/firstsales/free/llms.txt): $0.00 per 1,000, 33% complete, stored

## FirstSales's calls (1)

- `POST /api/v1/email/validate`: [FirstSales, free](https://datacircle.dev/validate-email-apis/firstsales/free/llms.txt)

## FirstSales's APIs (1)

- [FirstSales: email verification API pricing, 1 plan](https://datacircle.dev/validate-email-apis/firstsales/free/llms.txt)

## FirstSales: email verification API alternatives

- [KaijuVerifier, free, POST /api/v1/jobs, Submit an async bulk job](https://datacircle.dev/validate-email-apis/kaijuverifier/free-post-api-v1-jobs-submit-an-async-bulk-job/llms.txt): $0.00 per 1,000, 50% complete, stored
- [MailSift, free, GET /verify, Verify one email](https://datacircle.dev/validate-email-apis/mailsift/free-get-verify-verify-one-email/llms.txt): $0.00 per 1,000, 67% complete, stored (MX, SPF, DMARC: live)
- [Byteplant, free trial, POST /api/bulk-verify](https://datacircle.dev/validate-email-apis/byteplant/free-trial-post-api-bulk-verify/llms.txt): $0.00 per 1,000, 17% complete, stored
- [EasyEmailAPI, free](https://datacircle.dev/validate-email-apis/easyemailapi/free/llms.txt): $0.00 per 1,000, 67% complete, stored (valid MX, MX: live)
- [Interzoid, free API key, POST /enrich](https://datacircle.dev/validate-email-apis/interzoid/free-api-key-post-enrich/llms.txt): $0.00 per 1,000, 50% complete, stored

## Sources

From each provider's own pricing page and docs, and from what providers tell us. We read this row from these pages on 2026-10-23.

- https://firstsales.io/api/llms.txt
- https://firstsales.io/developers.md
- https://firstsales.io/developers/
- https://firstsales.io/llms.txt
- https://firstsales.io/openapi.json
- https://firstsales.io/pricing.md
- https://firstsales.io/pricing/
- https://firstsales.io/terms-of-service/