openmailserver is an open-source, self-hostable mail server for agents. Run your own mail infrastructure, provision inboxes on your own domain, and send and receive mail through an HTTP API, a CLI, and a containerized mox runtime.

• Self-host mail for agents instead of relying on shared SaaS inboxes.
• Generate inboxes and mailbox API keys for agent workflows and test environments.
• Send outbound mail from your own domain and read replies back through the API.
• Create local aliases like [email protected] and sync them into the runtime.

Open Mailserver separates the mail control plane from the mail runtime:

• the API and CLI provision mailboxes, aliases, API keys, and operational state
• mox handles SMTP, IMAP, and direct-to-MX delivery
• Postgres stores control-plane data and outbound metadata
• Docker Compose runs the stack together as api, postgres, and mox

That gives you a self-hosted mail stack that agents can drive through API calls or the CLI, while you keep the domain, runtime, and mailbox lifecycle under your control.

Prerequisites:

• git
• Python 3.11+ with venv
• Docker with Compose v2

Then run:

git clone https://github.com/openfrens/openmailserver
cd openmailserver
python3 -m venv .venv
.venv/bin/python -m pip install -e ".[dev]"
.venv/bin/openmailserver preflight
.venv/bin/openmailserver install
.venv/bin/openmailserver mox-quickstart
docker compose up -d
.venv/bin/openmailserver doctor

After the stack is up:

.venv/bin/openmailserver create-mailbox agent yourdomain.com
curl http://127.0.0.1:8787/health
.venv/bin/openmailserver smoke-test
.venv/bin/openmailserver plan-dns

By default, the stack publishes the API and web interfaces on host ports 8787, 80, and 443. To change those binds, see the installation docs for the supported reverse-proxy deployment flow.

Use a real domain from the start. Public internet delivery is not ready until MX, SPF, DKIM, DMARC, reverse DNS, and reachable mail ports are in place.

For full install details, Linux/macOS notes, and troubleshooting, see docs/install.md.

• Open Mailserver is built for direct-to-MX mail delivery.
• For public sending, prefer a Linux Docker host with direct access to ports 25, 80, and 443.
• Reverse DNS / PTR is controlled by the provider that owns the server IP.
• A fresh domain or IP may still land in spam until sender reputation improves.

• Tested on Binary Lane. Outbound mail may require disabling port blocking in mPanel first.
• OVHcloud VPS is commonly used for self-hosted mail and generally exposes port 25, but may block spammy IPs at the network level.
• Hetzner Cloud can work, but new cloud servers often need support approval before outbound mail ports are opened.
• UpCloud can open outbound port 25 on request after account verification.
• Exoscale restricts SMTP by default and requires enabling access in the provider portal.
• Akamai / Linode may restrict outbound SMTP on newer accounts and can require a support request.

Provider policies change often. Before you deploy, verify outbound mail port access, reverse DNS support, and abuse-policy fit for your use case.

• docs/README.md: docs index
• docs/install.md: install and first-run flow
• docs/api.md: mailbox provisioning, send, and read APIs
• docs/dns.md: required DNS records
• docs/deliverability.md: warmup and inbox placement
• docs/operations.md: backups and troubleshooting
• docs/security.md: security defaults
• docs/architecture.md: high-level architecture

make install
make run
make lint
make test

MIT. See LICENSE.