What the upgrade involved

The installer no longer ships the classic Administrator. The .NET 8 Control Panel is the sole bundled GUI and needs the .NET 8 Desktop Runtime, which the installer carries and installs silently when missing. DBSetup, DBUpdater and the Data Directory Synchronizer are retained.

Sieve and ManageSieve

• RFC 5228 parser covering if/elsif/else/stop, the core tests (header, address, exists, size, allof, anyof, not, with :is/:contains/:matches), address parts, the default and i;octet comparators, and keep/fileinto/discard/redirect plus implicit keep.
• Evaluated during local delivery. An account with no script has zero overhead. An unparseable script is logged and falls through to keep rather than breaking delivery.
• Scripts stored per account under {DataDirectory}\Sieve\{domain}\{localpart}\ and exposed as Account.SieveScript, Utilities.CheckSieveSyntax and Utilities.EvaluateSieveScript. The account dialog gained a Sieve editor tab.
• ManageSieve listener on [Settings] ManageSieveServerPort, disabled by default, with SASL PLAIN against the normal account database.

SMTP

• BATV (prvs) backscatter protection, wire-only so SPF and DKIM stay aligned. Off by default via BATVEnabled / BATVSecret.
• CHUNKING / BDAT (RFC 3030). DATA after BDAT is rejected 503, a non-numeric chunk size 501. The existing DATA path is untouched.

Operability

• /livez, /readyz and /healthz on the metrics listener, plus Prometheus series for pool state, query latency, TLS handshakes, auth success and failure, delivery outcomes and command latency.
• New keys, all defaulting to 0: SlowQueryLogMilliseconds, ShutdownDrainSeconds, MessageStoreFsync, MessageStoreConsistencyCheck, LogDeleteDays.
• The Received header now carries an RFC 5321 id clause equal to the numeric TCP session id, and that id prefixes every line of the session log.

Full release notes, checksums and signatures