hMailServer 6.0.0-B1

Pre-release

Released 12 June 2026 6.0 series

This is not the current release. hMailServer 6.3.3 is the one to install unless you need this exact version.

Downloads for 6.0.0-B1

Windows

Windows 10 (version 1607 or later) and Windows 11, or Windows Server 2016 and newer; 64-bit only. Run the installer as an administrator: it upgrades an installation older than this version in place, and it cannot go backwards — an older server refuses a database a newer one has upgraded, so back up the database and the data directory first. It is not Authenticode-signed, so Windows names an unknown publisher and SmartScreen warns before it will run it.

  • hMailServer-6.0.0-B1-x64.exex64 · 7.4 MB
    Download
    SHA-25686252bd2fe4e…cb16bfcd

What’s new in 6.0.0-B1

Modernized hMailServer 6.0 - first regression-validated build.

Full release notes for 6.0.0-B1

Toolchain: VS2026 (v145), OpenSSL 4.0.1, Boost 1.91, PostgreSQL 18.3 libpq, .NET Framework 4.8.1. Database version 6001 (upgrade from 5.7 supported via DBUpdater).

New in 6.0: MTA-STS + DANE/DNSSEC outbound TLS policy, ARC sealing, TLS-RPT reporting, ACME (Let's Encrypt) with auto-apply, REST admin API, MTA-STS/autoconfig/autodiscover hosting, Prometheus metrics, JSON logging, PBKDF2 password hashing with transparent rehash, Ed25519 DKIM, DMARC, IMAP MOVE/ID/SPECIAL-USE, 8BITMIME, Administrator dashboard + TOTP 2FA, TLS 1.2/1.3 defaults.

Validation: full regression suite - 898 tests, 895 passed, 0 code failures. Validated with live SpamAssassin (JAM Windows build), ClamAV 1.5.2 and all optional features enabled. The 3 non-passing tests are environment-bound: 2 require an unfiltered DNS resolver for SURBL test queries, 1 requires the service-based SpamAssassin variant. Includes fix for a latent CStdStr::FormatV buffer-count bug that crashed the service.

Install: run the installer; internal database (SQL CE 4.0) or external MySQL/MSSQL/PostgreSQL. See IMPLEMENTATION-NOTES.md for the feature/INI reference.

License: AGPLv3. Based on hMailServer by Martin Knafve.

Release facts

Version
6.0.0-B1pre-release
Packages
1Windows, x86-64
Installer SHA-256
86252bd2fe4e…cb16bfcdhMailServer-6.0.0-B1-x64.exe

Every file in 6.0.0-B1

Full SHA-256 of each file as recomputed on this server. Nothing in this release is signed — the signing workflow came later — so the hash above is this server’s own recomputation rather than a check against something the project signed.

FileWhat it isSizeSHA-256Signature
hMailServer-6.0.0-B1-x64.exeWindows installer · x647.4 MB86252bd2fe4e107cea374b3cd7353c4fb26d4e53ad5c57a608e8a2d0cb16bfcd—