# Postio, free: Email verification API

> Postio email validation goes past a regex: it checks syntax, resolves MX records and runs a live SMTP probe, then rolls the signals into one deliverability verdict — with flags for disposable, role and free-provider addresses.

Postio's email verification API on its 100 free lookups plan. It costs $0.00 per 1,000 emails. It returns 2 of the 6 key fields we check: Address, Deliverability.
In [our email verification API benchmark](https://datacircle.dev/best-email-verification-api.txt), the best plan from Postio scores 0.0 out of 100. Postio ranks 167th of 181 providers.
This plan is free. We rank 3,753 plans for email verification APIs by price. Half the plans cost $1.98 per 1,000 emails or less.
[treg's top-up from $10](https://datacircle.dev/validate-email-apis/treg/top-up-from-10/llms.txt) is the cheapest paid plan per 1,000 emails: $0.00 on average. treg asks one provider after another until one answers. You pay $68.365 per 1,000 emails when no provider answers.
[Disify's $9 monthly plan (/email)](https://datacircle.dev/validate-email-apis/disify/9-monthly-starter-post-email/llms.txt) covers any number of emails. Disify's $9 monthly plan costs less up front than treg's top-up from $10.
[MailTester Ninja](https://datacircle.dev/validate-email-apis/mailtester-ninja/23-99-monthly/llms.txt), [Enrich.so](https://datacircle.dev/validate-email-apis/enrich-so/499-monthly/llms.txt) and [GetProspect](https://datacircle.dev/validate-email-apis/getprospect/369-pack/llms.txt) are the best email verification API providers in the Datacircle benchmark.

- This page: https://datacircle.dev/validate-email-apis/postio/free
- [Email validation API: 180+ verification providers compared](https://datacircle.dev/best-email-verification-api.txt)
- Get it: https://postio.co.uk/pricing?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=email-verification-api-pricing
- Request: `GET https://api.postio.co.uk/v1/email/{address}`
- API key: with the plan, on https://postio.co.uk/pricing?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=email-verification-api-pricing
- Its API docs: https://postio.co.uk/docs/email?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=email-verification-api-pricing
- Sold by: Postio (https://postio.co.uk?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=email-verification-api-pricing)
- Checked: 2026-11-03

## In the answer

- Completeness: 33%
- Address: ✓
- Deliverability: ✓

## Price

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

## Aggregators

- Aggregators: none

## Not found

- $ per 1,000: $0.00

## In their words

- Their pitch: Postio email validation goes past a regex: it checks syntax, resolves MX records and runs a live SMTP probe, then rolls the signals into one deliverability verdict — with flags for disposable, role and free-provider addresses.

## Data

- Freshness: stored
- What it checks: format, mail servers, disposable domains, role addresses
- Keep data: no limit
- Use data: Don't use the API for fraud, spam targeting, stalking, harassment, or anything that breaks UK law. Because the address service uses Royal Mail PAF data, you must also keep to the PAF End User Terms — in particular, don't copy, extract, resell, republish or publicly display PAF data except as those terms allow, don't use it to build a competing product, and don't try to reverse-engineer the underlying data files. Don't use automated means to scrape or bulk-harvest responses beyond your purchased lookups.

## Plan

- Pay: $0
- You get: 100 requests
- Enough for: 100 calls

## Rate limit

- Per second: 30
- Batch: 1

## Speed

- Answer: in the call

## The call

- You send: address
- Method: GET
- Path: /email/{address}

## About the plan

- Plan: 100 free lookups
- Who can get it: anyone

## The 15 fields the plan's answer can hold

success, email address, valid syntax, did you mean, disposable, free provider, role account, MX found, SMTP check, catch-all, deliverability, result count, request ID, worker time, lookup time

## Postio's plans (2)

- [Postio, free](https://datacircle.dev/validate-email-apis/postio/free/llms.txt): $0.00 per 1,000, 33% complete, stored
- [Postio, top-up from £10](https://datacircle.dev/validate-email-apis/postio/top-up-from-10/llms.txt): $13.335 per 1,000, 33% complete, stored

## Postio's calls for this API (1)

- `GET /email/{address}`: [Postio, free](https://datacircle.dev/validate-email-apis/postio/free/llms.txt)

## Postio's APIs (2)

- [Postio: email verification API pricing, 2 plans](https://datacircle.dev/validate-email-apis/postio/free/llms.txt)
- [Postio: phone validation API pricing, 2 plans](https://datacircle.dev/validate-phone-apis/postio/free/llms.txt)

## Postio: email verification API alternatives

- [SendPulse, $61 pack, Pay As You Go 5,000, POST /verifier-service/send-single-to-verify/](https://datacircle.dev/validate-email-apis/sendpulse/61-pack-pay-as-you-go-5000-post-verifier-service-send-single-to-verify/llms.txt): $12.20 per 1,000, 33% complete, stored
- [Byteplant, $661 monthly, Monthly, 50,000 credits, GET /api/verify](https://datacircle.dev/validate-email-apis/byteplant/661-monthly-monthly-50000-credits-get-api-verify/llms.txt): $13.22 per 1,000, 17% complete, stored
- [TrustPath, €50 monthly](https://datacircle.dev/validate-email-apis/trustpath/50-monthly/llms.txt): $14.066 per 1,000, 67% complete, stored
- [DaData, ₽1,190,000 yearly](https://datacircle.dev/validate-email-apis/dadata/1190000-yearly/llms.txt): $14.207 per 1,000, 33% 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 2026-11-03.

- https://postio.co.uk?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=email-verification-api-pricing
- https://postio.co.uk/docs/email?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=email-verification-api-pricing
- https://postio.co.uk/docs/errors?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=email-verification-api-pricing
- https://postio.co.uk/docs/faq?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=email-verification-api-pricing
- https://postio.co.uk/docs/reference?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=email-verification-api-pricing
- https://postio.co.uk/openapi.json?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=email-verification-api-pricing
- https://postio.co.uk/pricing?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=email-verification-api-pricing
- https://postio.co.uk/terms?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=email-verification-api-pricing