A full mail stack in one Docker container: SMTP, IMAP, DKIM/DMARC, spam filtering, a REST API with Python & Node SDKs, and an MCP server for AI agents. Test email exactly as it behaves in production — or deploy it as a real mail server.
One container replaces an entire email infrastructure. SQLite works out of the box, while PostgreSQL is available for larger production workloads.
Accepts mail for any address on any domain. Nothing ever leaves the container. Safe by default.
Full Dovecot server with STARTTLS and implicit TLS. Use Thunderbird, mutt, or any standard client.
OpenDKIM signing, OpenDMARC verification, and SPF policy checks. Validate email authentication end-to-end.
SpamAssassin scores every inbound message. Configurable thresholds with Bayesian filtering and RBL checks.
Generate, import, and manage GPG keys per mailbox. Sign, encrypt, verify, and decrypt emails per RFC 3156.
A complete JSON API with an OpenAPI 3.1 spec, plus official Python (PyPI) and Node (npm) SDKs. Built for CI/CD.
An official Model Context Protocol server gives an AI agent its own mailbox to read, search, send, and triage email.
React-based interface with mailbox sidebar, folder navigation, rich email viewer, and HTML compose editor.
Server-Sent Events stream pushes email.received, email.deleted, mailbox.created, and more live.
Per-user isolated mailboxes with quotas. Scoped X-API-Key permissions restrict each key to specific actions and mailboxes.
Add custom domains with automatic DKIM. A DNS dashboard verifies MX, SPF, DKIM, DMARC, MTA-STS, and TLS-RPT records.
Flip MAILCUE_MODE=production for a hardened mail server: strict domains, enforced TLS, DMARC reject, and Let's Encrypt certs.
Capture outbound SMS, voice, and chat API traffic with wire-identical endpoints and signed webhooks for full end-to-end tests.
A built-in request inspector. Point any webhook at a bin URL and inspect method, headers, query, and body in real time.
Start with SQLite and optional AES-256 encryption, or connect PostgreSQL for concurrent production workloads and larger datasets.
Production-grade open-source components, assembled into a cohesive testing platform.
A comprehensive REST API with OpenAPI 3.1 spec and Postman collection included. Authenticate with JWT or scoped API keys, or reach for the official SDKs.
Send, receive, inject, bulk-inject, search, and manage emails programmatically.
Create, delete, and query mailboxes with folder statistics and email listings.
JWT login with optional TOTP 2FA, plus API keys scoped to specific actions and mailboxes.
Generate, import, export, and publish PGP keys. Full RFC 3156 PGP/MIME support.
Manage email domains with DKIM, DNS verification dashboard, TLS certs, and server settings.
Official Python and Node SDKs wrap the API, and an MCP server gives an AI agent its own mailbox.
Learn how to configure, integrate, and deploy MailCue for testing or production environments.
Container layout, request flow, and deep dive into Postfix, Dovecot, and Python FastAPI stacks.
Configure MailCue using environment variables, PostgreSQL or SQLite, network settings, and exposed ports.
Complete REST endpoint list, authentication methods, and scoped API key details.
Set up hardened mail server mode, PostgreSQL deployment and migration, DNS records, and TLS certificates.
Bypass port-25 blocks on cloud providers with a secure, authenticated SMTP egress tunnel.
Connecting email clients (Thunderbird, Mutt) over IMAP/POP3/SMTP and trusting custom CAs.
How to spin up MailCue in CI pipelines (GitHub Actions, GitLab CI) for end-to-end tests.
Official MCP server documentation to equip AI agents with mailboxes and email capabilities.
Mock SMS, voice, and chat APIs (like Twilio or Slack) and inspect webhooks in real time.
Running a single container behind a shared Docker network to communicate across multiple local projects.
Setting up local development, running tests, linting, and the pull request workflow.
One command. No signup. No configuration. A full email server at your fingertips.