Sendmail Sentrion Open Source is an enterprise-grade open-source email server for large, complex environments, offering DKIM authentication to protect against email fraud and ensure message integrity.

---

🚀 Overview

Sendmail Sentrion Open Source is a powerful, scalable open-source Mail Transfer Agent (MTA) derived from Proofpoint's commercial Sentrion platform. It delivers enterprise-level email handling capabilities tailored for demanding production environments.

What problem does this project solve? It addresses the challenges of managing high-volume, complex email infrastructures, including virtualization, server consolidation, and cloud migrations, while providing robust security through DKIM signing and verification to combat fraud and spoofing.

Who is it built for? Large organizations and sysadmins needing a reliable open-source email server with long-term support and enterprise scalability.

Why did you build it? Proofpoint released a subset of their proven Sentrion platform as open source to empower the community with production-ready tools, bridging open-source simplicity with enterprise reliability.

---

✨ Key Features

• DKIM digital signing of messages to verify origin and integrity, crucial for preventing phishing and email fraud.
• Cryptography-based sender authentication that safeguards organizational brand and reputation.
• Scalable design optimized for large-scale deployments, supporting virtualization, consolidation, and cloud transitions.
• Optional: PGP-signed releases and integration with OpenDKIM for advanced filtering.

---

🛠 Tech Stack

• Backend: Sendmail platform (version 8.18.2), OpenDKIM (forked from dkim-milter 2.8.3)
• Language: C libraries for DKIM-aware applications and milters
• Security: PGP/GPG for release signing
• Deployment: Self-hosted on Linux/Unix systems

---

👥 Who Is This For?

This project is useful for:

• Sysadmins and developers managing enterprise email servers
• Teams handling complex messaging infrastructures and migrations
• Organizations seeking open-source alternatives to proprietary MTAs

---

📸 Screenshots / Demo

• Live demo: https://ftp.sendmail.org/pub/sendmail/ (latest release downloads)
• GitHub: https://github.com/Distrotech/sendmail (source mirror)

---

🔥 Project Status

• 🟡 Maintained

Last updated: 2025-12-27

---

❓ FAQ

Is this project free?

Yes / Open Source (Free to download, use, modify, and distribute under open-source license.)

---

Is the source code available?

Yes — Official releases at https://ftp.sendmail.org/pub/sendmail/sendmail.8.18.2.tar.gz (PGP sig: https://ftp.sendmail.org/pub/sendmail/sendmail.8.18.2.tar.gz.sig); GitHub mirror: https://github.com/Distrotech/sendmail

---

Can I contribute?

Submit bugs to sendmail-bugs@support.sendmail.org, patches/features/general comments to sendmail@support.sendmail.org, security issues to sendmail-security@support.sendmail.org. Discuss on comp.mail.sendmail newsgroup. Check FAQ and README first.

---

📬 Contact & Links

• Website: https://www.proofpoint.com/us/products/email-protection/open-source-email-solution
• GitHub: https://github.com/Distrotech/sendmail
• Twitter/X: https://x.com/proofpoint
• Email: sendmail-bugs@support.sendmail.org (bugs), sendmail-security@support.sendmail.org (security), see site for full list

---

Built with ❤️ and kept warm on WarmIndex.