Email firewall open source

Here are some popular open-source email firewalls:

1. Postfix: A widely used open-source mail transfer agent (MTA) that can be configured as an email firewall. It provides features like spam filtering, virus scanning, and content filtering.
2. Sendmail: Another popular open-source MTA that can be used as an email firewall. It provides features like spam filtering, virus scanning, and content filtering.
3. OpenSMTPD: A modern, open-source MTA that provides features like spam filtering, virus scanning, and content filtering. It's designed to be highly configurable and scalable.
4. MailScanner: A free, open-source email scanner that can be used as an email firewall. It provides features like spam filtering, virus scanning, and content filtering.
5. SpamAssassin: A popular open-source spam filtering system that can be used as an email firewall. It provides features like spam filtering, virus scanning, and content filtering.
6. ClamAV: A free, open-source antivirus engine that can be used as an email firewall. It provides features like virus scanning and malware detection.
7. Suricata: An open-source intrusion detection and prevention system (IDPS) that can be used as an email firewall. It provides features like network traffic analysis, protocol analysis, and attack detection.
8. OpenWRT: A popular open-source router firmware that provides features like email firewalling, spam filtering, and virus scanning.
9. pfSense: A popular open-source firewall that provides features like email firewalling, spam filtering, and virus scanning.
10. Endian Firewall: A free, open-source firewall that provides features like email firewalling, spam filtering, and virus scanning.

These are just a few examples of open-source email firewalls. Each has its own strengths and weaknesses, and the choice of which one to use will depend on your specific needs and requirements.

Here are some key features to consider when evaluating an open-source email firewall:

• Spam filtering: Can the firewall detect and block spam emails?
• Virus scanning: Can the firewall detect and block viruses and malware?
• Content filtering: Can the firewall filter out specific types of content, such as attachments or specific keywords?
• Network traffic analysis: Can the firewall analyze network traffic to detect and block suspicious activity?
• Protocol analysis: Can the firewall analyze network protocols to detect and block suspicious activity?
• Attack detection: Can the firewall detect and block specific types of attacks, such as denial-of-service (DoS) or distributed denial-of-service (DDoS) attacks?
• Scalability: Can the firewall handle a large volume of email traffic?
• Customizability: Can the firewall be customized to meet specific needs and requirements?

It's important to evaluate each option carefully and consider factors like ease of use, scalability, and customizability when choosing an open-source email firewall.