Mailosaur

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Introduction

Mailosaur lets teams ‘preview, test and trust every customer touchpoint’, according to its homepage. It provides unlimited test email addresses on Mailosaur domains, dedicated phone numbers for SMS, and real-device previews of emails in clients such as Gmail and Outlook.

The main testing use case is validating flows that depend on messages: sign-ups, password resets, one-time passwords and multi-factor authentication. Tests send to a Mailosaur address or number, then use the API or an official library to wait for the message, read its content and extract links or codes.

Mailosaur can also act as a dummy SMTP server to catch all mail from an application, and it supports rules that simulate bounces and out-of-office replies. Libraries and plugins exist for Cypress, Playwright and several languages.

In the quality loop, it covers end-to-end checks of email and SMS flows.

Features

1. Test inboxes: Unlimited addresses on Mailosaur domains.
2. SMS testing: Dedicated numbers for OTP and MFA tests.
3. Device previews: See emails in Gmail, Outlook and mobile clients.
4. Dummy SMTP: Catch every email an app sends.
5. Automation APIs: Libraries and plugins for common frameworks.
6. Scenario rules: Simulate bounces and auto-replies.

Pros

1. Email plus SMS: Covers both channels in one service.

Cons

1. No free plan listed: Paid plans start at $20 per month billed annually.
2. Hosted only: No self-hosted option.

Usage and Links (Example)

// Cypress with the cypress-mailosaur plugin
cy.mailosaurGetMessage(serverId, { sentTo: "signup@" + serverDomain })
  .then((email) => {
    expect(email.subject).to.equal("Confirm your account");
    cy.visit(email.html.links[0].href);
  });

Resources:

• Mailosaur website

Pricing

Plans from $20 per month (billed annually); higher tiers and enterprise plans available. See site.

Recommended for?

1. Teams testing OTP, MFA and email flows end to end.
2. Not a fit if you only need local email capture.

Conclusion

Mailosaur is a focused, well-integrated service for email and SMS testing in automated suites.

On CheckOps, Mailosaur is filed under the End-to-end & functional and Integration testing stages. Related tools listed here include Mailtrap, MailSlurp, Mailpit, Cypress, Playwright and Selenium. Before choosing, compare them on licence, supported languages and platforms, hosting model, and how well each fits your existing CI pipeline. Facts on this page were checked against the official website, documentation and repository on 11 November 2026; statements the vendor makes about its own product are marked as vendor claims.