Sendmail is a general-purpose internetwork email routing facility that supports many kinds of mail-transfer and delivery methods, including the Simple Mail Transfer Protocol (SMTP) used for email transport over the Internet. Sendmail has a long history dating back to 1983 and was the default MTA for many Unix systems.
- Latest Stable: 8.18.2 (December 27, 2025)
- Previous: 8.18.1, 8.17.2 (legacy)
- Download: ftp.sendmail.org
- Maintainer: Proofpoint, Inc.
- Flexible Routing: Sophisticated mail routing and rewriting rules
- Protocol Support: SMTP, ESMTP, various delivery protocols
- Mailing Lists: Built-in mailing list support
- Configuration: Highly configurable via sendmail.cf
- Security: Authentication, TLS encryption support
- Enterprise Features: Commercial support via Proofpoint
- Compatibility: Backward compatible with legacy configurations
- Legacy Systems: Maintaining existing Unix infrastructure
- Enterprise Environments: Proofpoint-supported deployments
- Complex Routing: Environments requiring sophisticated mail routing
- Historical Interest: Learning email system evolution
- Language: C
- Architecture: Monolithic with modular configuration
- OS Support: Unix, Linux, BSD, macOS
- Dependencies: Standard Unix libraries, OpenSSL for TLS
- Sendmail License (permissive open source)
- Commercial License: Available via Proofpoint
- ⚠️ Legacy Status - Still maintained but largely replaced by Postfix/Exim
- ✅ Security Updates - Regular security patches from Proofpoint
- ⚠️ Complex Configuration - Steeper learning curve than modern alternatives
- ⚠️ Declining Usage - Most distributions now default to Postfix or Exim
Community Docker images are available for Sendmail:
# Example: Basic Sendmail container
docker run -d \
--name sendmail \
-p 25:25 \
-e MAILNAME=example.com \
somecommunity/sendmail:latest
Note: No official Docker image exists. Consider using Postfix or Exim for Docker deployments.
Sendmail was originally developed at UC Berkeley in the 1980s and became the standard mail transfer agent for Unix systems. In 2004, Proofpoint acquired Sendmail, Inc. and continues to maintain the open-source version while offering enterprise products.
- 1983: First released as part of 4.2BSD
- 1990s: Dominant MTA for Unix systems
- 2000: Sendmail, Inc. founded
- 2004: Acquired by Proofpoint
- 2025: Version 8.18.2 released with modern security features
¶ History and References
- Official Website: https://www.proofpoint.com/us/products/email-protection/open-source-email-solution
- Documentation: Included in package (sendmail-doc)
- Download: ftp.sendmail.org
- Commercial Support: Proofpoint, Inc.
Common issues and solutions:
- Complex configuration: Use m4 macros to generate sendmail.cf
- Performance: Consider tuning queue settings for high-volume sites
- Security: Regular updates essential; consider Postfix for new deployments
👉 See Sendmail Configuration for detailed configuration guidance.
Any questions?
Feel free to contact us. Find all contact information on our contact page.