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Postio.co.uk VS StackMail

Compare Postio.co.uk VS StackMail and see what are their differences

Postio.co.uk

Fast UK address, email & phone validation APIs for developers. Official Royal Mail PAF data. Pay as you go, 100 free lookups.

Rating
0 reviews
Pricing
Paid Free trial £0.02 (Address 2.2p (searching is free), Email & Phone 1p)
Alternatives Is it good?
StackMail

Stackmail is a webmail service whereby you can log in to your emails from any browser at any time!

Rating
0 reviews
Alternatives Is it good?
SpinUp
Business email without the bloat. sponsored
Note: These products don't have any matching categories. If you think this is a mistake, please edit the details of one of the products and suggest appropriate categories.

Which is more popular?

Address Verification API popularity
100% vs 0%
alternatives listed
11 vs 1

Base details

Website, pricing, platforms and company facts side by side.

Postio.co.uk
StackMail
Website postio.co.uk stackmail.com
Pricing
Paid Free trial £0.02 (Address 2.2p (searching is free), Email & Phone 1p) Official pricing
—
Platforms
REST API Web JavaScript Node JS Python Go PHP Ruby .Net Wordpress Zapier +8
—
Company Startup from the United Kingdom · 1 - 9 employees —
Listed in
Address Finder Address Verification API Postcode API Email Verification API Phone Number Validation +2
Email Email Service Provider Hosted Email Email Clients +1

About Postio.co.uk and StackMail

In their own words, as submitted to SaaSHub.

Postio.co.uk
StackMail

Postio (postio.co.uk) is a developer-focused data validation platform providing real-time UK address lookup, email verification, and phone validation via plain REST APIs and drop-in SDKs. As an official Royal Mail PAF Solutions Provider, Postio synchronises 30M+ UK addresses daily for accurate...

Read more about Postio.co.uk

No description of StackMail yet.

Features and specs

What each product offers, as listed by its team.

Postio.co.uk 9 features
StackMail 5 features
  • Address search
    UK address typeahead over Royal Mail PAF data, held under a direct licence
  • Postcode lookup
    Every PAF delivery point at a given postcode
  • UDPRN lookup
    Full address record by Royal Mail Unique Delivery Point Reference Number
  • Email validation
    Syntax, typo correction, MX, SMTP check and deliverability classification
  • Phone validation
    Parse and validate, plus live HLR lookup for carrier, ported status and reachability
  • Pricing model
    Pay per request — 2.2p per address, 1p per email, 1p per phone. No tiers, no contracts
  • Free tier
    100 lookups, no card required
  • API design
    All endpoints are GET and return the same JSON envelope. Public OpenAPI spec, CORS enabled
  • SDKs and integrations
    Official SDKs for JavaScript/Node, Python, Go, PHP, Ruby and .NET. Drop-in browser widget (~4 KB gzipped), MCP server for AI agentsOfficial SDKs for JavaScript/Node, Python, Go, PHP, Ruby and .NET. Drop-in browser widget (~4 KB gzipped), MCP server for AI agents
  • Privacy-Focused
    StackMail emphasizes data privacy and security, offering encrypted email services without scanning user data for advertising purposes, appealing to privacy-conscious businesses.
  • Business-Oriented Features
    Designed specifically for businesses, it includes features like custom domain email, collaborative tools, calendars, and contact management tailored for professional use.
  • Competitive Pricing
    StackMail offers competitively priced plans compared to some larger email providers, making it accessible for small to medium-sized businesses.
  • No Ads
    Unlike some free email services, StackMail does not display ads to users, providing a cleaner and more professional email experience.
  • Custom Domain Support
    Users can easily set up email addresses with their own custom domain names, enhancing brand professionalism and consistency.

Possible disadvantages

  • Limited Brand Recognition
    As a newer or lesser-known provider compared to Google Workspace or Microsoft 365, StackMail may lack the trust and reputation that larger providers have established.
  • Fewer Third-Party Integrations
    Compared to major email service providers, StackMail may offer fewer integrations with third-party apps and services, limiting its versatility for some businesses.
  • Limited Advanced Features
    It may not offer the same breadth of advanced productivity and collaboration tools that come bundled with larger platforms like Microsoft 365 or Google Workspace.
  • Smaller User Community
    Due to a smaller user base, there may be fewer community resources, third-party tutorials, or troubleshooting forums available online.
  • Uncertain Long-Term Support
    As a smaller company, there might be concerns regarding the long-term viability, updates, and continued support of the service compared to more established providers.

Analysis

An editorial look at what each product does well and who it suits.

Postio.co.uk
StackMail

No analysis of Postio.co.uk yet.

Overall verdict

  • StackMail is a solid choice for individuals and businesses seeking a secure, ad-free, privacy-focused email hosting solution with reliable features at a competitive price point.

Why this product is good

  • Ad-free email experience with no data mining or tracking of user content
  • Custom domain email hosting suitable for professional and business use
  • Competitive pricing compared to major enterprise email providers
  • Includes essential productivity tools like calendar, contacts, and webmail access
  • Strong emphasis on privacy and security in data handling
  • Straightforward setup process for custom domains

Recommended for

  • Small to medium-sized businesses wanting professional email addresses
  • Privacy-conscious individuals and organizations
  • Startups looking for cost-effective email hosting
  • Users seeking an alternative to Google Workspace or Microsoft 365
  • Freelancers and entrepreneurs needing custom domain email

Category popularity

How often each product is chosen within a category, 0–100% relative to the other.

Score bands 0–20 21–40 41–50 51–60 61–100
Postio.co.uk
StackMail
100% 100%
Address Verification API
0% 0%
0% 0%
Email Clients
100% 100%
100% 100%
Phone Number Validation
0% 0%
0% 0%
Email
100% 100%

Questions & Answers

As answered by people managing Postio.co.uk and StackMail.

What makes your product unique?

Postio.co.uk's answer

Postio charges only when a lookup returns a result — searching is free. Address, email and phone validation sit behind one API with a single JSON response envelope, so you integrate once rather than stitching three vendors together. Address data comes from Royal Mail's Postcode Address File under a direct licence, not scraped or resold sources. There are no tiers, contracts or minimum spend, and the first 100 lookups need no card.

Which are the primary technologies used for building your product?

Postio.co.uk's answer

A REST API served from edge locations, with official SDKs for JavaScript/Node, Python, Go, PHP, Ruby and .NET, all open source on GitHub. The API is documented by a public OpenAPI specification.

Why should a person choose your product over its competitors?

Postio.co.uk's answer

Pricing is published and pay-as-you-go: 2.2p per address, 1p per email, 1p per phone, billed only on a result. No sales call, no annual contract, no minimum commitment. You can be live in a few minutes with 100 free lookups and no card, and the same API covers all three validation types. For UK addresses specifically, the data is licensed directly from Royal Mail rather than obtained second-hand — which matters after the 2025 High Court ruling on database rights in this market.

How would you describe the primary audience of your product?

Postio.co.uk's answer

Developers and technical teams building UK-facing forms — ecommerce checkouts, signup flows, CRM and logistics systems. Typically small to mid-sized product teams, agencies building for UK clients, and software vendors embedding address lookup in their own product. It suits anyone who wants a UK-accurate API without an enterprise procurement process.

What's the story behind your product?

Postio.co.uk's answer

Postio is a trading name of Onno Group Limited, registered in England & Wales (company no. 08622799). It was built to make Royal Mail PAF-accurate UK validation available on straightforward pay-as-you-go pricing, rather than the contracts and minimum commitments that have been standard in this market. Address, email and phone validation were brought together behind one consistent API so a team can solve all three at once.

Who are some of the biggest customers of your product?

Postio.co.uk's answer

Serving a huge range of customers across the world looking for a blazing fast UK Address AIP product. From bootsrapped entrepreuners to FTSE 250 companies. We serve them all.

User comments

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Alternatives to Postio.co.uk and StackMail

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