Mailu is a simple, full-featured, open-source mail server provided as a set of Docker images. It is designed to be easily set up and maintained while avoiding proprietary software or unrelated groupware features. It is entirely composed of FOSS components (Free and Open Source Software) and includes no tracker.

Here are the principal features and functionalities of Mailu:

1. Architecture and Setup

• Docker-Based Deployment: Mailu is deployed using a set of Docker images and can be set up using either Docker Compose or Kubernetes.

• Database Flexibility: It supports changing the database back-end and can integrate with external services like MySQL/MariaDB or PostgreSQL.

• DNS Requirements: Setup requires careful configuration of DNS settings, including MX entries, Reverse DNS entries, and DKIM/SPF & DMARC Entries.

• Reverse Proxy Support: It supports using an external reverse proxy like Traefik.

• Maintenance: Documentation covers maintaining the server, including upgrading, monitoring, and managing external Let's Encrypt certificates.

2. Standard and Advanced Email Capabilities

• Standard Protocols: Functions as a complete email server supporting IMAP and IMAP+ (for receiving), and SMTP and Submission (for sending).

• Client Configuration: Provides auto-configuration profiles for clients.

• Advanced Features: Supports aliases, domain aliases, and custom routing.

• Search: Includes full-text search of email attachments.

3. Security and Anti-Spam Measures

Mailu integrates numerous security and anti-spam features:

• Connection Security: Features enforced TLS (Transport Layer Security).

• Authentication & Trust: Supports modern standards like DANE, MTA-STS, and outgoing DKIM.

• Malware Protection: Includes an anti-virus scanner and Snuffleupagus. It can be configured to block malicious attachments.

• Spam Filtering: Features auto-learn capabilities, greylisting, and support for DMARC and SPF. It also implements anti-spoofing measures and allows blocking emails from specific domains.

• Certificates: Integrates Letsencrypt! for TLS certificate management.

4. User and Administration Interfaces

• Web Access: Provides multiple Webmails and a dedicated Web administration interface.

• Administrative Tools:

  • Supports setting quotas and defining global admins.

  • Allows per-domain delegation and sending announcements.

  • Provides specific web interface sections for managing anti-spam settings, mail domains, and relayed domains.

• Developer and Command Line Tools:

  • Offers a Mailu RESTful API with an in-built SwaggerUI.

  • Includes a dedicated Mailu command line interface for tasks like managing users, aliases, domains, and configuration (e.g., user, alias, config-update).

• End-User Management: Users can manage personal settings such as aliases, auto-reply, auto-forward, fetched accounts, and managesieve.