Haitatsu is a simple email server written in Go. It receives and stores mail, exposes IMAP and SMTP submission for clients, and provides a REST API for trusted backend services to manage mailboxes and messages.

• IMAP support
• SMTP support (inbound, outbound is via relay)
• REST API
• Automatic ACME certificates
• App passwords for protocol access.
• PostgreSQL for metadata, S3-compatible storage for message blobs
• Pkl-based hot-reloadable configuratiion.

Mailbox users do not call the REST API directly. Integrate from your own backend using a configured service token. End users authenticate to IMAP and SMTP with app passwords.

• Go 1.26 or later
• Pkl (for local runs outside Docker)
• PostgreSQL
• S3-compatible object storage (MinIO works for development)

Copy the example config and edit it for your environment:

cp haitatsu.example.pkl haitatsu.pkl

The server reads config from haitatsu.pkl by default. Override with -config path/to/haitatsu.pkl.

Start Postgres and MinIO, then build and run Haitatsu:

docker compose up -d postgres minio minio-init
task build
./haitatsu -config haitatsu.pkl

Or run the full stack (Postgres, MinIO, and Haitatsu in Docker):

task compose:up

The compose stack publishes:

Health checks: GET /health, GET /ready. Metrics: GET /metrics.

Stop the stack with task compose:down. Reset volumes with task compose:reset.