Erooster

A mail suite written in Rust, meant to be easy to use.

Features

IMAP (ports 143 / 993)

• IMAP4rev2 (RFC 9051) and IMAP4rev1 (RFC 3501) compatible
• TLS on port 993, STARTTLS on port 143
• Extensions: IDLE, NAMESPACE, UNSELECT, MOVE, ESEARCH, ENABLE, UTF8=ONLY
• AUTH=PLAIN over TLS

SMTP (port 25)

• STARTTLS
• Extensions: PIPELINING, SIZE, 8BITMIME, AUTH LOGIN PLAIN (over TLS), REQUIRETLS, VRFY
• DKIM signing on outbound messages (RSA PKCS#1 and PKCS#8)
• DKIM and DMARC verification on inbound messages
• SPF verification
• Optional Rspamd integration for spam filtering

General

• Maildir storage
• PostgreSQL (default) or SQLite backend
• Single binary, stable Rust
• Autoconfig endpoint (/mail/config-v1.1.xml) for automatic client setup (Thunderbird etc.)
• Optional Sentry error reporting

Non-goals

• MySQL / MariaDB support
• POP3
• Exchange / ActiveSync
• Every optional extension from every RFC

Getting started

Requirements

• TLS certificates in PEM format (e.g. from Let's Encrypt)
• DKIM key pair
• PostgreSQL database (or SQLite for testing)

Generate DKIM keys

opendkim-genkey \
    --domain=<your-hostname> \
    --subdomains

Save the .private file at the path you set in mail.dkim_key_path and add the generated TXT record to your DNS.

Configuration

Create config.yml in /etc/erooster/ or the working directory:

tls:
  key_path: "./certs/key.pem"
  cert_path: "./certs/cert.pem"
mail:
  maildir_folders: "./maildir"
  hostname: "example.com"
  displayname: "Erooster"
  dkim_key_path: "/etc/erooster/keys/default.private"
  dkim_key_selector: "default"
database:
  url: "postgres://user:password@localhost/erooster"
listen_ips:
  - "0.0.0.0"
  - "[::]"
webserver:
  port: 80
  tls: false
# Optional — remove if not using Rspamd
rspamd:
  address: http://localhost:11333

maildir_folders is the root directory where per-user mail is stored in Maildir format.

Run

cargo run --release

Or with SQLite (testing only):

cargo run --release --no-default-features --features sqlite

Manage users

Use the bundled eroosterctl binary. It reads the same config.yml.

# Create a new user
eroosterctl register

# Change a user's password
eroosterctl change-password

Passwords are stored as Argon2 hashes.

SQLite

SQLite is supported as a compile-time feature (--features sqlite) and is useful for local development and tests. It is not recommended for production — use PostgreSQL instead.

Support

Due to personal constraints, there is no enterprise support for Erooster. Please open GitHub issues instead. Responses are best-effort with no guaranteed time frame.

Error reporting

Erooster does not report errors automatically. A GitHub link is printed on panics. You can optionally configure a Sentry DSN via environment variable for self-hosted error reporting.