Test emails that never leave the warren.
MailWarren is a fake SMTP inbox for developers. Point your app at it in dev and staging, and every email gets safely burrowed away for you to inspect — instead of landing in a real customer's inbox.
Everything you need to stop guessing what your app is sending
Safe by default
Every outgoing email is captured in your warren, never delivered to a real inbox — swap one SMTP setting and stop worrying about test runs emailing real customers.
Inspect every detail
See the rendered HTML, plain text, headers, and attachments for each message — on a phone-sized screen or in a simulated dark mode.
Pre-send checks
A spam-risk score, how the email will hold up in Gmail, Outlook, Apple Mail and Yahoo, accessibility problems, and links that don't load — before a real customer sees it.
Share a burrow
Give your whole team a shared inbox per project or environment — no more forwarding screenshots in Slack.
Built for test automation
Wait for the email your app sent, read the verification code or link, and assert on it — from Playwright, Cypress, Jest, pytest or xUnit, with no sleeps. SDKs for JavaScript, Python and .NET, on every plan, Free included.
Made for AI agents
Connect Claude Code or any MCP client and let your agent send, read and check emails itself — “did the signup email go out, and is it right?”
See how test automation and the AI agent tools work →
Using an AI coding agent? Point it at mailwarren.io/llms.txt — the whole API, written for agents (also as OpenAPI).
Simple, transparent pricing
Start free. Upgrade when you need longer message history, more teammates or more volume — no contract, change or cancel any time.
- 200 captured messages / month
- Unlimited Warrens & mailboxes
- 1 MCP key
- Up to 3 team seats
- 1-day message retention
- Test API, SDK & MCP — 30 requests/min
- Spam, mail-client & accessibility checks
- 2,000 captured messages / month
- Unlimited Warrens & mailboxes
- 5 MCP keys
- Up to 10 team seats
- 30-day message retention
- Test API, SDK & MCP — 90 requests/min
- Live link checks — 25/day
- 20,000 captured messages / month
- Unlimited team seats & MCP keys
- 90-day message retention
- Priority support
- Test API, SDK & MCP — 240 requests/min
- Live link checks — 150/day
- 100,000 captured messages / month
- Unlimited team seats & MCP keys
- Unlimited message retention
- SSO & audit log coming soon
- Test API, SDK & MCP — 600 requests/min
- Live link checks — 600/day
- Bulk email campaigns — up to 25,000 contacts
Sending real email through your own verified domain uses prepaid credit, on any plan. Need SSO, custom limits or dedicated support? Choose Enterprise after you sign up and we'll be in touch.
Sign up freeReady to stop guessing what your app is sending?
Create an account in under a minute — solo, or bring your whole team along with an organisation account.