Sendmail Open Source

Sendmail Open Source is the open-source subset of Proofpoint's Sendmail Sentrion platform, designed for large and complex mail environments. The current Open Source release is Sendmail 8.16.1, distributed as a tar.gz archive with a PGP signature, and signed by the 2025 signing key. OpenDKIM is referenced as part of the Open Source offering.

Key Features

• Open Source subset of Sendmail Sentrion for enterprise-scale environments.
• Release 8.16.1 available on ftp.sendmail.org as a tar.gz archive with a PGP signature; signatures generated with the 2025 signing key.
• Includes OpenDKIM integration (DKIM) to authenticate messages.
• Security and licensing guidance, including CERT contact points and PGP signing keys.

Use Cases

• Deployments in large, complex mail infrastructures needing a durable open-source MTA with long-term manageability (virtualization, consolidation, cloud migration).
• Environments requiring verifiable, signed open-source builds from ftp.sendmail.org for audits and compliance.
• Setups needing DKIM-based mail signing and authentication controls.

Limitations and Considerations

• The Open Source option is a subset of the full Sendmail Sentrion offering; some enterprise features may be unavailable. Consult a specialist to assess fit.

Conclusion

Sendmail Open Source provides an officially supported open-source path for enterprise-style email deployments within the Sendmail Sentrion lineage. It offers a current release (8.16.1) with signed distributions and OpenDKIM support, suited for organizations able to manage an open-source MTA stack.