# FirstSales, free: Cached email verification API

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

FirstSales's cached 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.
FirstSales limits how many calls you get, but doesn't say how many.

- This page: https://datacircle.dev/cached-email-validation-apis/firstsales/free
- Get it: https://firstsales.io/developers/
- Its API docs: https://firstsales.io/developers/
- Sold by: FirstSales (https://firstsales.io)
- Checked: 2026-10-23

## In the answer

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

## Price

- $ per 1,000: $0.00
- Billing: free

## Aggregators

- Aggregators: none

## Charges

- Per: call
- 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

## 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/cached-email-validation-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/cached-email-validation-apis/firstsales/free/llms.txt)

## FirstSales's APIs (1)

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

## FirstSales: cached email verification API alternatives

- [graph8, free](https://datacircle.dev/cached-email-validation-apis/graph8/free/llms.txt): $0.00 per 1,000, 33% complete, stored
- [KaijuVerifier, free, Free, POST /api/v1/jobs](https://datacircle.dev/cached-email-validation-apis/kaijuverifier/free-free-post-api-v1-jobs/llms.txt): $0.00 per 1,000, 50% complete, stored
- [Strale, free, trial credits, POST /v1/do, Bulk Email Validation](https://datacircle.dev/cached-email-validation-apis/strale/free-trial-credits-post-v1-do-bulk-email-validation/llms.txt): $0.00 per 1,000, 50% complete, stored
- [APIVerve, free](https://datacircle.dev/cached-email-validation-apis/apiverve/free/llms.txt): $0.00 per 1,000, 50% complete, stored (MX valid, MX record, null MX, can receive mail, has SPF, has DMARC: 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 2026-10-23.

- 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/