Inbound mail from a Postfix-based relay could hang forever. The connection logs 354 OK, send., stops dead, and the sender eventually gives up with "timed out while sending end of data", leaving a zero-byte file in the Data folder. Anyone taking mail from Postfix or a Proxmox Mail Gateway was affected, and a same-host relay hits it almost every time. Three previous releases claimed to fix it and did not. This one was settled by running a real Postfix 3.10 against the server and reading the bytes on the wire. What the upgrade involved Two known issues stand. Equal-preference MX records are not randomised (RFC 5321 5.1); the server always tries them in the order the resolver returned, and a comment and COM help string that claimed otherwise have been corrected. One-click unsubscribe (RFC 8058) is not implemented. RFC 2369 List-* headers are still emitted for distribution-list postings. Changes Postfix pipelines the terminating dot and QUIT into one segment, so the terminator sits mid-buffer and every tail-only end-of-data check missed it. The receive path now searches for <CRLF>.<CRLF> anywhere in what arrived and returns the remainder to the command parser. Bare-LF terminators are still recognised only at the very end of the buffer, with anything behind them discarded, which is the CVE-2023-51764 rule. SMTP dot transparency (RFC 5321 4.5.2) now carries line-start context across buffer boundaries in both directions. Previously a line-leading dot landing a byte or two into a chunk went unstuffed, silently truncating messages. Sieve scripts were left behind by domain and account renames and deletes. Recreating an address could reactivate the previous holder's filter, redirects included. Renames now move the Sieve tree, deletes remove it, and the Control Panel writes the script only after the save succeeds. Sieve body test (RFC 5173) implemented and advertised over ManageSieve, with :text, :content and :raw. SORT () US-ASCII ALL spun a connection thread at 100% of a core forever. Empty sort criteria are now rejected per RFC 5256. The 512 MB message-list cache never evicted and only counted upwards. Eviction now measures entries as they are. Malformed DNS answers are retried once over TCP. The Control Panel MX tool (#29) now uses the server's resolver via Utilities.ResolveMXRecords. Control Panel: seven Administrator functions restored, plus Welcome page icon alignment (#30). Everything in the 6.2.20 notes is in this release too. Full release notes, checksums and signatures

Fresh installations of this build failed. Database creation broke on the built-in SQL Server Compact backend, which is the default, and most likely on MySQL, and a silent install then hung on a hidden message box instead of reporting the failure. Upgrades of existing installations were unaffected. 6.2.20 fixed both. For anyone already running it: if a custom DNS server was configured, every DNS lookup hMailServer made had been failing since 6.2.16. This release fixed that. Installations with no custom DNS server were never affected, because the server list is only built when one is set. 6.2.16 moved name resolution onto the asynchronous DnsQueryEx and gave the custom-DNS-server entry a destination port of 53. A DNS_ADDR carries a full SOCKADDR, so setting the port looks correct. It is not: the DNS client supplies the port itself, and with port 53 every query returns status 87 and no records. MX lookups for outbound delivery, DNSBL, SPF and SURBL all failed. It surfaced loudest as HM5507 The IP address for SpamAssassin could not be resolved, which is how #25 came in. A regression test now points DNSServer at TEST-NET-1 (192.0.2.1) and requires the lookup to time out; a timeout proves a packet left the machine. What the upgrade involved The database schema moves from 6005 to 6011. DBUpdater applies it. Take a backup first. Settings are preserved. The [Settings] INI values move into the database for remote administration; the file still wins where both carry a value. Also in this release Active Directory can now create accounts, not just link them. Settings.PreviewDirectorySync and Settings.ApplyDirectorySync read an LDAP directory and create or update the mailboxes it says should exist, with a Control Panel page and an optional unattended schedule. A domain takes part only if its Active Directory domain name is set, so provisioning is opt-in per domain. Nothing is ever deleted. Sieve imap4flags now reaches the message. setflag, addflag, removeflag and the :flags tag were parsed and evaluated, then discarded at delivery. They are now applied to the stored message, and imap4flags has moved into the ManageSieve capability line. Only the five system flags can be stored; a keyword is logged rather than dropped in silence. GetUniqueMessageID could hand out the same UID twice, which makes a client show one message in place of another. An account address containing a colon accepted mail at RCPT TO, then failed when the message was filed: the local part becomes a directory name in the message store. Known issue: #26, partial FETCH BODY[]<offset.length> against 6.2.18, does not reproduce here against new tests that reassemble whole messages from chunks over FETCH and UID FETCH. If you can still reproduce it, post an IMAP protocol log. Full release notes, checksums and signatures

6.2.3 is the first server-focused release since 6.2.2, which shipped Control Panel changes against an unchanged server. The headline is a complete Sieve filtering subsystem (RFC 5228) with an optional ManageSieve service (RFC 5804), running alongside the existing proprietary rules engine. Every new behaviour is additive and default-off, so an existing installation upgraded with no functional change until the new settings were turned on. 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