OpenSMTPD

Self-Hosted

Secure, lightweight open-source Mail Transfer Agent

Overview

OpenSMTPD is a free, open-source MTA built for simplicity and security, adhering to RFC standards. It features human-readable configuration files, TLS encryption for secure communication, SPF/DKIM anti-spam support, and compatibility with Unix-like systems (Linux, BSD). Deployable via package managers or Docker containers, it balances core MTA functionality with minimal attack surface, making it ideal for small to medium self-hosted email servers.

Self-Hosting Resources

Find Official Image on Docker Hub View Source & Docs

Below is a reference structure for docker-compose.yml. ⚠️ Do NOT run blindly. Replace placeholders with official values.

docker-compose.template.yml TEMPLATE


version: '3'
services:
  opensmtpd:
    image: <OFFICIAL_IMAGE_NAME>:latest
    container_name: opensmtpd
    ports:
      - "8080:<APP_INTERNAL_PORT>"
    volumes:
      - ./data:/app/data
    restart: unless-stopped

Key Features

Simple human-readable configuration files
TLS encryption & full RFC compliance
SPF/DKIM anti-spam integration
Unix-like system compatibility (Linux, BSD)

Frequently Asked Questions

? Is OpenSMTPD hard to install?

OpenSMTPD is easy to install on Unix-like systems via package managers (apt, pkg, etc.) or Docker containers. Configuration uses simple, human-readable files, so beginners with basic sysadmin skills can set it up quickly.

? Is it a good alternative to managed email services like Google Workspace?

Yes—OpenSMTPD is perfect for users wanting full control over their email infrastructure. It avoids vendor lock-in and ensures data privacy, though it requires more hands-on maintenance than fully managed SaaS services.

? Is it completely free?

Absolutely! OpenSMTPD is released under the ISC license, making it fully free and open-source for personal or commercial use with no restrictions or paid tiers.

Top Alternatives

Microsoft Exchange Online Search Google

Google Workspace Search Google

Amazon SES Search Google

Tool Info

Pricing Free/Open Source

Category Communication - Email - Mail Transfer Agents

Platform Self-Hosted

Pros

⊕ Lightweight with minimal attack surface
⊕ Easy to configure for beginners
⊕ Fully open-source (ISC license, no hidden costs)

Cons

⊖ Requires basic Unix system administration knowledge
⊖ Limited advanced features compared to Postfix
⊖ No built-in web interface for management