Exim is a powerful and flexible Mail Transfer Agent (MTA) for Unix-like systems connected to the Internet. Originally developed at the University of Cambridge, Exim provides extensive facilities for checking incoming mail and is designed to be installed as a replacement for Sendmail, though with a significantly different configuration approach.
- Latest Stable: 4.99.1 (December 2025)
- Security Release: Addresses CVE-2025-67896 (remote heap corruption)
- Previous Versions: All versions before 4.99.1 are obsolete
- Flexible Mail Routing: Sophisticated routing capabilities with extensive configuration options
- Advanced Filtering: Comprehensive facilities for checking and filtering incoming mail
- Security-Focused: Built-in security features and privilege management
- Standards Compliance: Full support for SMTP, IMAP, POP3, and modern email standards
- Extensible Architecture: Modular design supporting custom transports and lookups
- Detailed Logging: Comprehensive logging and diagnostic capabilities
- Self-Hosted Email Infrastructure: Complete email server solutions
- Mail Routing and Delivery: Sophisticated routing for complex environments
- Relay Services: Secure mail relay for multiple domains
- Academic/Enterprise Environments: Custom routing rules and policies
- High-Volume Mail Systems: Scalable architecture for large deployments
- Language: C
- Architecture: Modular with pluggable transports and lookups
- OS Support: Unix-like systems (Linux, BSD variants)
- Dependencies: Standard Unix libraries, OpenSSL for TLS support
- GPL-2.0 (GNU General Public License v2.0)
- Actively maintained with regular security updates
- Latest version 4.99.1 addresses critical security vulnerabilities
- Recommended for environments requiring flexible mail routing
¶ History and References
- Version 4.99.1: Security update - upgrade immediately if using older versions
- Configuration Changes: Review documentation for any breaking changes in new versions
- Security Improvements: Enhanced privilege management and security hardening options
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