Mailosaur

What Mailosaur does

Mailosaur Ltd is a privately held UK SaaS company, registered in England and Wales (Companies House no. 07999725), that operates a cloud-based email and SMS testing platform for engineering, QA, product management, and marketing teams. The platform combines three core products — Email Testing (automated end-to-end email verification using virtual SMTP servers and catch-all test addresses), SMS Testing (dedicated phone numbers and secure delivery for OTP, MFA, and transactional message testing), and Email Previews (rendering validation on real devices and email clients including Gmail and Outlook, with light/dark mode coverage) — augmented by feature modules such as Rules, Custom Domains, Enterprise SSO/SCIM, Forwarding Rules, Links and Codes, and Message Analysis. The underlying technology is a cloud-hosted virtual SMTP and SMS infrastructure with a REST API, eight official SDKs (Node.js, Java, Ruby, Python, .NET, PHP, Go, JavaScript), and native integrations with 12+ testing frameworks including Cypress, Playwright, Selenium, Robot Framework, Postman, Cucumber, TestCafe, WebdriverIO, Ghost Inspector, Insomnia, and PowerShell. The platform is hosted on Google Cloud EMEA infrastructure and holds ISO 27001:2022, PCI DSS, SOC 2, GDPR, UK GDPR, and CCPA certifications.

Mailosaur operates an API-first, product-led growth go-to-market: a 14-day free trial with no credit card converts to Self-Service Plans with automatic renewal, complemented by an enterprise sales motion for Managed/Enterprise contracts with SSO, custom pricing, and SLA guarantees. Pricing is tiered (Personal, Core, Enterprise) on monthly and annual cadences, with enterprise pricing not publicly disclosed. The customer base spans large global enterprises (Uber, PayPal, Forbes, UEFA, Domino's, Aer Lingus, Charlotte Tilbury, Checkout.com, Malwarebytes, OakNorth) alongside a long tail of SMB and individual subscribers attracted via SEO, developer documentation, and case-study content marketing. The company is bootstrapped (no disclosed funding rounds), has a stated headcount of 1-10, and is led by co-founder and CEO Jonathan Mahoney.

Name

Mailosaur

Legal name

Mailosaur Ltd

Website

https://mailosaur.com

Company type

Private

Founded year

2013

Operating status

Operating

Headcount range

11–50 employees

Short description

Mailosaur is a UK-based SaaS platform that provides automated email, SMS, and MFA testing for engineering, QA, product, and marketing teams via API, SDKs, and integrations with major testing frameworks. It serves both self-serve developers and enterprise customers such as Uber, PayPal, and UEFA.

Ownership category

akta.pro rank

Headquarters

HQ city

Basingstoke

HQ country

United Kingdom

HQ region

Europe

Offices1 record

Markets served

GTM type

B2B

Offering type

Software

Cost components

Technology or R&D, Infrastructure, Personnel, Marketing or Sales, Operations

Revenue model

1. Subscription Plans: Mailosaur generates revenue through tiered subscription plans (Personal, Core, Enterprise) with monthly and annual billing options. Plans differ in email and SMS allowances, number of seats, and feature access (e.g., SSO requires Enterprise). The 14-day free trial converts to paid subscriptions automatically for Self-Service Plans, while Managed Plans require manual renewal approval.

Pricing tiers

Go-to-market motion2 records

Distribution channels3 records

Marketing channels6 records

Core offering

Mailosaur provides a cloud-based platform for automated email and SMS testing, enabling engineering and QA teams to capture, inspect, and validate messages sent by their applications within CI/CD pipelines. The platform offers dedicated test inboxes, virtual SMTP servers, real-device email rendering previews, and a REST API with SDKs in eight programming languages, alongside native integrations with testing frameworks such as Cypress, Playwright, and Selenium. Customers use the platform to verify transactional flows including sign-ups, password resets, MFA/OTP codes, and marketing email rendering across clients and devices.

Product overview

Mailosaur is a unified email and SMS testing platform designed for QA, engineering, and product teams. The core product portfolio consists of three main offerings: Email Testing (for automated end-to-end email testing with unlimited test addresses and virtual SMTP servers), SMS Testing (for automated SMS/OTP testing with dedicated phone numbers), and Email Previews (for rendering validation on real devices and email clients). These core products are augmented by feature modules including Virtual SMTP Servers (catch-all email interception), Rules (automated scenario simulation), Custom Domains (branded test addresses), Enterprise SSO/SCIM (enterprise identity integration), Forwarding Rules, Links and Codes verification, and Message Analysis. The platform provides native integrations with major testing frameworks (Cypress, Playwright, Selenium) and supports SDKs in 8 programming languages, enabling automated testing workflows within CI/CD pipelines.

Differentiator

Problem solved

Functional benefit

Products and services

• Email Testing

Quantifiable outcome

• 99.99% uptime maintained over 90 days
• +1 more outcomes

Named customers17 records

Segments4 records

Ideal customer profiles2 records

Technology focussed Yes

API detail

Has API

Yes

API docs

API detail

Core technology

AI maturity

App detail

Integration19 records

AI capability5 records

Feature10 records

Partnerships

Ten partnerships are on record, tiered core.

• CypresscoreTechnology or IntegrationOfficial integration partner providing native Cypress support for email and SMS testing automation. Mailosaur provides documentation and code samples for seamless integration into Cypress test suites.
• PlaywrightcoreTechnology or IntegrationNative Playwright integration for end-to-end email and SMS testing. Includes quickstart guides and dedicated documentation for automating message testing.
• SeleniumcoreTechnology or IntegrationComprehensive Selenium integration for email testing with dedicated quickstart guides and automation documentation.
• Ghost InspectorcoreTechnology or IntegrationIntegration partner for automated website testing combined with Mailosaur email/SMS testing capabilities.
• Robot FrameworkcoreTechnology or IntegrationPython-based open source automation framework integration with official Mailosaur Python library support.
• PostmancoreTechnology or IntegrationOfficial Postman Collection available for API testing with Mailosaur, allowing developers to test email/SMS via Postman's API platform.
• OktacoreTechnology or IntegrationSSO/SCIM integration allowing enterprise customers to use Okta identity management with Mailosaur.
• Microsoft EntracoreTechnology or IntegrationSSO/SCIM integration for Microsoft Entra (Azure AD) identity management, enabling enterprise customers to provision and manage Mailosaur access.
• Google Cloud EMEA LimitedcoreTechnology or IntegrationPrimary cloud infrastructure provider hosting Mailosaur servers in EU/UK data centers with security-focused configuration.
• Stripe, Inc.coreTechnology or IntegrationPayment processing provider for subscription billing and invoicing. Processes customer payments securely.

Scale indicators2 records

Recent moves6 records

Expansion highlights5 records

Emerging players

• smtp4dev: Open-source SMTP server for development and testing, popular in .NET environments — another free alternative that addresses a subset of Mailosaur's email-capture use case.
• MailHog: Long-standing open-source SMTP testing tool popular with Go developers; provides email capture and inspection without SaaS pricing — represents the free, self-hosted alternative to Mailosaur.
• Mailpit: Open-source email testing tool with a modern UI for SMTP capture and HTML viewing — competes in the same email-testing sandbox category as Mailosaur, primarily serving self-hosting and SMB use cases.

Direct peers

• MailSlurp: MailSlurp provides disposable email inboxes and SMS phone numbers for automated testing, including OTP verification — directly comparable in product offering and target developer/QA persona.
• Mailtrap: Mailtrap is the closest direct competitor, offering a virtual inbox/SMTP sandbox for dev and QA teams to inspect and test emails in automated workflows — overlapping customer base, feature set, and developer-first GTM.

Broad incumbents

• BrowserStack: Larger, well-funded cross-browser and device testing platform serving enterprise QA teams; while not a direct email-testing competitor, it sits in the same QA budget and could expand to absorb Mailosaur's category.
• Sauce Labs: Enterprise continuous testing cloud covering browser, mobile, and API testing; competes for the same QA tooling budget and could bundle email/SMS testing capabilities.

Others

• Cypress: End-to-end testing framework and a core Mailosaur integration partner; while not a direct competitor, Cypress could in theory bundle native email/SMS testing features into its platform, posing strategic risk.
• Postmark: Transactional email delivery provider with adjacent developer audience; comparable customer base of product/engineering teams building notification-heavy applications, though focused on sending rather than testing.
• TestRail: Test case management platform widely used by the same QA teams that buy Mailosaur — not a direct competitor but adjacent tooling in the same enterprise QA buying center.

Market position

Strengths5 records

Weaknesses5 records

Competitive moat4 records

Key risks6 records

Key highlights7 records

Customer concentration

• Xx.com/mailosaur

Compliance5 records

Revenue estimate

Valuation estimate

Number of profiles

Profiles1 record

Funding overview

Funding rounds

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Mailosaur