OpenSMTPD
OpenSMTPD is an open source SMTP server daemon for Linux and BSD operating systems. It aims to be a free, secure, and featureful SMTP server for both hosting providers and end users.
smtp
mail-server
email
linux
bsd
open-source
OpenSMTPD: Free & Secure SMTP Server for Linux & BSD
OpenSMTPD is an open source SMTP server daemon for Linux and BSD operating systems. It aims to be a free, secure, and featureful SMTP server for both hosting providers and end users.
What is OpenSMTPD?
OpenSMTPD is an open source SMTP server daemon for Linux and BSD operating systems. It was created in 2015 as a secure alternative to existing SMTP server solutions.
Key features of OpenSMTPD include:
- Support for the SMTP, SMTP over TLS (SMTPS), and SMTP over SSL (SMTP/SSL) protocols
- Modular and secure codebase written in C language
- Built-in support for DKIM (DomainKeys Identified Mail) email signing and verification
- Flexible configuration through text files, no database required
- Virtual hosting for running multiple domains from one server
- IP address and domain name access control lists for security
- Compatibility with common SMTP authentication mechanisms like CRAM-MD5, LOGIN, and PLAIN
OpenSMTPD is commonly used by hosting providers, companies, and enthusiasts who want an open source, easy-to-configure SMTP solution with good security defaults. Its modular architecture makes it customizable for advanced users as well.
OpenSMTPD Features
Features
- Open source SMTP server
- Supports SMTP over TLS/SSL
- Milter support for spam and virus filtering
- Daemon mode for background operation
- IPv4 and IPv6 support
- SMTP AUTH login, plain and cram-md5
- STARTTLS support
- DKIM signing and verification
- SMTP pipelining
- Queue control and delivery modes
- Virtual domains and users
- SMTP client mode
Pricing
- Open Source
Pros
Free and open source
Secure - supports encryption and authentication
Extensible and customizable via filters
Lightweight and high performance
Cross-platform - runs on Linux and BSD
Cons
Limited user interface/admin dashboard
Steeper learning curve than commercial options
Requires more technical expertise to setup and manage
Lacks some enterprise features found in commercial SMTP servers
Official Links
The Best OpenSMTPD Alternatives
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