This is the first build of the modernised 6.0 line to clear the full regression suite: 898 tests, 895 passed, 0 code failures.

What the upgrade involved

Database version was 6001. Upgrade from 5.7 was supported via DBUpdater.

Toolchain for this build: VS2026 (v145), OpenSSL 4.0.1, Boost 1.91, PostgreSQL 18.3 libpq, .NET Framework 4.8.1.

What 6.0 brings in:

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

Fixed in this build: a latent CStdStr::FormatV buffer-count bug that crashed the service.

Validation ran with live SpamAssassin (JAM Windows build), ClamAV 1.5.2 and all optional features enabled. The three non-passing tests are environment-bound rather than code defects. Two require an unfiltered DNS resolver for SURBL test queries, and one requires the service-based SpamAssassin variant.

Installation is via the installer, against the internal database (SQL CE 4.0) or an external MySQL, MSSQL or PostgreSQL instance. IMPLEMENTATION-NOTES.md carries the feature and INI reference.

Licensed AGPLv3. Based on hMailServer by Martin Knafve.

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