# Mailsac

> Mailsac is an email testing service for developers and QA teams. It gives you test inboxes you can read over a REST API, so automated tests and CI/CD pipelines can check that signup verification, password reset, magic link and one-time code emails arrive and work. Public @mailsac.com inboxes need no setup; paid plans add private addresses and private test domains (your own domain or a zero-setup *.msdc.co subdomain), webhooks, WebSockets, team logins with SAML SSO, and higher volume.

Key facts:
- Every address at @mailsac.com already exists and receives mail; there is nothing to create first. These public inboxes can be read by anyone, so use made-up data. Private addresses and private domains keep test mail visible only to your account.
- REST API at https://mailsac.com/api, authenticated with the `Mailsac-Key` header. List messages: `GET /api/addresses/{email}/messages`. Read plain text: `GET /api/text/{email}/{messageId}`. Delete: `DELETE /api/addresses/{email}/messages/{messageId}`.
- Email Capture is a fake SMTP relay (capture.mailsac.com, port 5587, STARTTLS, Mailsac username and API key): point a test environment's SMTP settings at it and every message is kept in Mailsac instead of being delivered.
- Mailsac can also test real delivery: your app sends through its normal email provider to a Mailsac address or private domain, which catches provider, DNS, SPF/DKIM and sending-domain problems that a local SMTP catcher cannot.
- Push instead of polling: webhooks, WebSockets and Slack forwarding deliver each new email as it arrives.
- AI coding agents: the official MCP server `@mailsac/mcp` (npm, MIT) gives Claude Code, Cursor, VS Code, Claude Desktop and other MCP clients tools to create a test address, wait for an email and read its links and one-time codes. Install for Claude Code: `claude mcp add mailsac -e MAILSAC_API_KEY=your-key -- npx -y @mailsac/mcp`; other clients run `npx -y @mailsac/mcp` over stdio with `MAILSAC_API_KEY` set.
- Usage is counted in operations (one API call, one inbound email to a private address or domain, or one push).
- Plans (USD): Free (1,500 operations/month); Indie $18/month for one developer (25,000 operations); Business $89/month for teams (500,000 operations, 5 users, SAML SSO); Business+ $199/month (2 million operations, 10 users, invoice or purchase order on annual); Enterprise from $7,500/year or $799/month (2–20M+ operations, 25 users, security reviews, purchase orders and resellers).

## Get started
- [Email testing API overview](https://mailsac.com/pages/email-testing-api/): how testing signup and password-reset emails with Mailsac works, limits and plans
- [Email testing in CI/CD example (GitHub)](https://github.com/mailsac/mailsac-integration-test-examples/tree/main/playwright-signup-ci): runnable Playwright test of a signup verification email in GitHub Actions and GitLab CI
- [Email testing in CI/CD: step-by-step guide with GitHub Actions and GitLab CI](https://blog.mailsac.com/integrating-email-testing-into-your-ci-cd-pipeline-a-step-by-step-guide/)
- [Playwright email testing guide](https://blog.mailsac.com/playwright-email-testing/)
- [Cypress email testing guide](https://mailsac.com/pages/cypress-email-testing/): read signup codes, password-reset links and magic links in Cypress tests with @mailsac/cypress or cy.request; GitHub Actions and parallel runs
- [Test email OTP codes and magic links](https://mailsac.com/pages/test-otp-and-magic-link-emails/): get the one-time code or magic link from an email in Playwright, Cypress, Python and Selenium tests, with a reusable wait-for-email helper and fixes for flaky tests
- [Private email domain for testing](https://mailsac.com/pages/private-test-email-domain/): a zero-DNS yourteam.msdc.co subdomain or your own domain (TXT + 2 MX records) for staging and CI; any address works without setup
- [Cypress plugin @mailsac/cypress](https://www.npmjs.com/package/@mailsac/cypress)
- [Mailsac MCP server @mailsac/mcp](https://www.npmjs.com/package/@mailsac/mcp): test inboxes for AI coding agents (Claude Code, Cursor, VS Code, Claude Desktop); tools create_test_address, wait_for_email, list_emails, read_email, delete_emails, list_domains
- [MCP server setup guide](https://docs.mailsac.com/en/latest/services/mcp_server/mcp_server.html) and [announcement](https://blog.mailsac.com/mailsac-mcp-server/); source on [GitHub](https://github.com/mailsac/mailsac-mcp)
- [Pricing](https://mailsac.com/pricing)

## Documentation
- [Docs home](https://docs.mailsac.com/en/latest/)
- [REST API reference](https://mailsac.com/docs/api)
- [Email Capture (fake SMTP relay)](https://docs.mailsac.com/en/latest/services/email_capture/email_capture.html)
- [Custom and private domains](https://docs.mailsac.com/en/latest/services/private_domains/private_domains.html)
- [Webhooks and forwarding](https://docs.mailsac.com/en/latest/services/forwarding/forwarding.html)
- [Subscriptions and billing FAQ](https://docs.mailsac.com/en/latest/help/subscriptions/faq.html)

## Comparisons
- [Mailsac vs Mailosaur](https://mailsac.com/pages/mailsac-vs-mailosaur/)
- [Mailsac vs Mailtrap](https://mailsac.com/pages/mailsac-vs-mailtrap/)
- [Mailsac vs MailSlurp](https://mailsac.com/pages/mailsac-vs-mailslurp/)
- [Mailsac vs Mailpit and MailHog](https://mailsac.com/pages/mailsac-vs-mailpit/)
- [Mailsac vs Mailinator](https://mailsac.com/pages/mailsac-vs-mailinator/)
- [Mailsac vs testmail.app](https://mailsac.com/pages/mailsac-vs-testmail/)
- [Mailsac vs Mailisk](https://mailsac.com/pages/mailsac-vs-mailisk/)
- [Email load testing: receive thousands of test emails in a burst](https://mailsac.com/pages/email-load-testing/)

## Optional
- [Temp mail: a free temporary email address in the browser, no signup](https://mailsac.com/temp-mail)
- [Enterprise: procurement, security reviews, resellers](https://mailsac.com/enterprise)
- [Blog](https://blog.mailsac.com/)
- [Status page](https://status.mailsac.com/)