This was an alpha. Everything in it shipped in 6.2.24. Nothing here should be installed today. Thunderbird 128 and later could not save a single Sent copy. Every message went out over SMTP and nothing was ever stored, with only a per-machine client setting as a workaround (GitHub issue 53). Two ways a sender could steer the anti-spam tests are also closed here. What the upgrade involved This is an alpha because one of the fixes changes what a non-conforming client sees. Relayed and fetched mail is now tested against a different address. The Received parser takes the last observed address before by, ignores values marked as HELO-supplied, and keeps a header whose host name is not a valid domain name. If you sit behind an incoming relay and have tuned scores around the old behaviour, expect verdicts to move. MAIL FROM straight after a STARTTLS handshake with no fresh EHLO now gets 503 Bad sequence of commands, as RFC 3207 section 4.2 requires. If you have a home-grown submission script that skips the second EHLO, this is the release that tells you. Changes IMAP APPEND: once a client enables UTF8=ACCEPT, RFC 6855 lets it wrap the message as UTF8 (~{n} plus a closing ). The parser counted parentheses across the whole line and refused with BAD APPEND Command requires at least 2 parameter before reading a byte. The wrapper is now stripped ahead of the parser, including the non-synchronizing ~{n+} form and later messages of a MULTIAPPEND. Anti-spam bypass: the parser took the first bracketed value after from, which is the HELO literal the client chose, and skipped any header whose host name was not a valid domain (my_pc). DNSBL, SPF and the HELO-host test could be skipped entirely. Two assert(0) on sender-reachable input are gone with it. RSET before EHLO no longer opens a transaction on its own. That had let MAIL FROM through with an empty HELO host, skipping the OnHELO/OnEHLO events. A PTR answer carrying the trailing dot (1.0.0.127.in-addr.arpa.) no longer empties the result. That had been failing open in the HELO and reverse-DNS spam tests. hMailServer.exe is built with /guard:cf in both configurations (GitHub issue 45). An unattended install whose database step fails now fails, rather than showing a suppressible message box and exiting 0. Known limitation: the weekly C++ CodeQL analysis has not run since late August. It targets a self-hosted runner that is no longer registered. Full release notes, checksums and signatures

This was an alpha. Everything in it shipped in 6.2.24. Nothing here should be installed today. Local delivery could lose a message with no trace. When the account-level copy could not be written, LocalDelivery reported HM5209 and returned, but the recipient row was deleted anyway and the queued message with it. The sender had already been given 250 and the recipient never heard of it. Anyone running a message store near full was exposed. The sender is now told. This is an alpha. Do not put it on a production mail server. What the upgrade involved The schema moves 6022 to 6025 in three registered steps, and it is one way. An older server refuses to run against a newer dbversion, so rollback needs a pre-upgrade database backup and a data-directory backup. The 6024 to 6025 step widens hm_messages.messageflags from tinyint to smallint on MS SQL, SQL CE and MySQL/MariaDB. That is a table rewrite on your largest table, holding locks throughout. Size the maintenance window to your hm_messages row count. PostgreSQL is unaffected. Silent upgrades with /VERYSILENT previously hung forever on a modal password dialog. Fixed. Five COM properties added during the 6.2.22 pre-releases were declared mid-interface, shifting the vtable on AntiSpam, Account, Application and GlobalObjects. They are appended now, restoring binary compatibility with 6.2.21. Late-bound scripts were never affected. Recompile anything early-bound against a 6.2.22 pre-release. Three new defaults change behaviour. MinimumFreeDiskSpaceMB=100 refuses new mail below the floor, 452 4.3.1 at MAIL FROM and NO [UNAVAILABLE] at IMAP APPEND. WindowsEventLogEnabled=1 forwards errors to the Windows Application log under the source hMailServer. DatabaseStatementTimeout=30 is untested on MySQL and PostgreSQL, the two backends it was built for. Existing per-account out-of-office replies now apply RFC 3834 suppression and stop answering bounces, list traffic and anything carrying Auto-Submitted or List-* headers. Also in this release PROXY protocol v1/v2 and XCLIENT in front of SMTP, so DNSBL, SPF, greylisting and auto-ban see the real client. Both ship off with empty trust lists. Shared and delegated IMAP mailboxes at #[email protected], gated on RFC 4314 ACLs. On by default, enableimapacl ships as 1. RFC 3030 BINARYMIME. Relay of a binary message is refused 554 5.6.3 rather than converted. RFC 3464 bounces. Every NDR is now multipart/report. Re-check anything parsing whole bounce bodies. External HTTP filtering hook (FilterHookUrl, FilterHookTimeoutSeconds default 10), plain HTTP only. Sender blacklist, per-account spam thresholds, distribution-list moderation, domain-wide out-of-office, IPv6 on the REST and metrics listeners. Full release notes, checksums and signatures

This was the last pre-release in the 6.2.22 line. Everything in it shipped in 6.2.24. Nothing here should be installed today. pre4 was withdrawn. Its installer could not create its own database: two SQL statements were written on consecutive lines, the script parser splits commands on a blank line, and SQL Server Compact, which a default install uses, rejected the pair as one command. The install succeeded, the service started, and it listened on nothing. Anyone who ran a fresh pre4 install was affected. The v6.2.22-pre4 tag still exists but has no release. Do not build from it. What the upgrade involved This is pre-alpha. Nobody has run it on a production server, and the installer is smoke-tested on a throwaway CI runner only. Use a spare box. Upgrading from pre3 requires DBUpdater: the schema moves from 6019 to 6022 in three steps. DMARC, brought up to DMARCbis The DNS tree walk (RFC 9989 §4.10) replaces the Public Suffix List for deciding organizational domain. Bounded at eight queries per domain, cached five minutes. DmarcTreeWalkEnabled=0 keeps the list, which is also used whenever a lookup fails transiently. The np= tag (RFC 9989 §5.5.4) is honoured, so the resolver now reports the RCODE to tell NXDOMAIN from NODATA. Aggregate reports now emit the DKIM <selector> and SPF <scope> from RFC 7489, never sent before. Algorithms DKIM rsa-sha1 is refused (RFC 8301), on signing and verification. A domain configured to sign with it is signed rsa-sha256 instead and told so. DkimAcceptSha1=1 restores both halves. DKIM keys below 1024 bits are refused (RFC 8301 §3.2). SPF void lookups are capped at two (RFC 7208 §4.6.4). SpfVoidLookupLimit to change or disable. Certificates and delivery ACME renewal begins two thirds through the certificate's lifetime with a one-day floor, instead of a fixed 30 days. ARI (RFC 9773) is consulted hourly and the CA's window wins when offered, clamped to a day before expiry. A full mailbox is refused at RCPT with 452 4.2.2, ending the backscatter to forged envelope senders. RejectFullMailboxAtRcpt=0 restores the old behaviour. QuotaWarningPercent (default 90, 0 disables) sends one notice per crossing. Schema 6022. Operations Per-domain outbound relay, GitHub discussion 31. Order is route, then the sending domain's relay, then the server-wide relayer. Schema 6021. Queryable message trace, off by default. Schema 6020. ArchiveRetentionDays prunes ArchiveDir, 0 by default, .eml files only. The DMARCbis aggregate-report namespace (RFC 9990) is not implemented. Reports remain the RFC 7489 form. Full release notes, checksums and signatures

This was the third pre-release in the 6.2.22 line. Everything in it shipped in 6.2.24. Nothing here should be installed today. Per-account two-factor authentication now works at the server. TOTP has been in this product for years and protected exactly one thing: the Control Panel's own logon, checked after the server had already accepted the password. The server had no idea the feature existed. It does now (schema 6017). Once a secret is enrolled, the account password stops being a mailbox credential and an app password becomes the only one. What the upgrade involved Upgrading from pre2 requires DBUpdater. The database schema moves from 6015 to 6019 in four steps. Password expiry ships with a caveat: this server has no self-service password change, so an expired password can only be reset by an administrator. Existing app passwords keep working, Active Directory accounts are exempt, and an unreadable stamp is never treated as expired. App passwords (schema 6016). A per-account credential, revocable on its own, that authenticates over IMAP, POP3 and SMTP alongside the account's own password. 20 symbols from a 30-character alphabet, about 98 bits, from OpenSSL's CSPRNG. They are tried only after the account password has failed. Password policy. IsStrongPassword has existed for years and nothing in the server has ever called it. Every mailbox on every installation could be test. Five settings now decide, plus one rule that is always on: a password may not contain the account name. Enforced where a password is chosen, never where an existing one is verified. Quarantine (schema 6018). Refused messages can now be held in a store an administrator can list, read, release or delete, with a review queue in the Control Panel. Quarantining answers 250 instead of 550, so the sender will not retry and this store is the only place the message exists. A quarantine that fails to store falls through to refusing. Off by default. IMAP and POP3. FETCH BINARY on a composite section returned an empty literal and BINARY.SIZE agreed with it. Documented as a limitation in pre2, fixed here. BINARY now announces content with literal8 (~{n}) as RFC 3516 requires. POP3 answers EXPIRE with NEVER and can enforce LOGIN-DELAY (RFC 2449). Off by default. OAuth2. ES256 tokens now verify. JWS carries an ECDSA signature as a raw R||S pair while OpenSSL verifies X9.62 DER. A key that does not match the algorithm named is refused on the key type. A valid ES256 token is still refused while the allow-list omits it. Full release notes, checksums and signatures

This was the second pre-release in the 6.2.22 line. Everything in it shipped in 6.2.24. Nothing here should be installed today. hMailServer has consumed DMARC policy for years and produced nothing for the domains whose mail it receives. This pre-release adds DMARC aggregate reporting (rua, RFC 7489). Every evaluation is aggregated per UTC day and per policy domain, passes included, and the Appendix C XML is mailed to the addresses a domain asks for with rua=. It stays inert until DmarcRptFromAddress is set. What the upgrade involved The database schema moves to 6015. Upgrading from pre1 requires DBUpdater. Known limitations: FETCH BINARY on a composite section returns an empty literal, so BINARY[], multipart and message/rfc822 sections come back empty (leaf parts are correct). DMARC report data lives in memory, so a restart before the daily send loses that day's statistics. Reporting RFC 7489 §7.1 external-destination verification is enforced. A rua target outside the policy domain's own organizational domain is used only when <policy-domain>._report._dmarc.<target-domain> says it wants the reports. Forensic (ruf) reports are deliberately not implemented. Utilities.SendTlsRptReports(IncludeCurrentDay) and its twin SendDmarcReports send what has been collected so far, not just days that are over. Both refuse, statistics preserved, when the From address is unset. Authentication AccountLockoutThreshold counts failures by the name being guessed at, so a distributed attack that never crosses any single IP's auto-ban threshold is still caught. Off by default, enforced on every path including SCRAM. A locked name gets the ordinary invalid-credentials reply, and that refusal is kept out of the per-IP auto-ban. POP3 AUTH-RESP-CODE (RFC 3206): credential failures carry [AUTH], a failed inbox load carries [SYS/TEMP]. A transient database problem made scheduled clients nag for a password that was never wrong. Anti-virus A scan that could not run was delivered with one line in the error log, indistinguishable from a clean scan. AVFailAction 0 (the default) keeps today's behaviour. 1 holds the message, re-attempts it and returns it to the sender rather than delivering it unscanned. IMAP BINARY (RFC 3516) decodes a part's Content-Transfer-Encoding server-side, and APPEND accepts the literal8 (~{n}) form. OBJECTID (RFC 8474): EMAILID follows a message through copies, MAILBOXID survives RENAME, THREADID is answered NIL. Fixes /Test no longer terminates on an unhandled exception when the machine has no network or a third party's DNS breaks. An idle server stops in about half a second rather than up to two. Nine settings reachable only by editing the ini now have Control Panel fields. Full release notes, checksums and signatures

This was the first pre-release in the 6.2.22 line. Everything in it shipped in 6.2.24. Nothing here should be installed today. The built-in ACME client has never completed an order against a real Let's Encrypt. If you issued certificates through hMailServer rather than an external client, it failed every time. That is fixed here (GitHub issue 34). What the upgrade involved This is a pre-release. Take a backup before installing it. Databases upgrade automatically from schema 6012 to 6014 via the bundled DBUpdater. ACME (GitHub issue 34) Boulder, the software behind Let's Encrypt staging and production, pretty-prints its JSON: "type": "http-01", with a space after the colon. The challenge locator searched for the compact form, "type":"http-01", which can never match a real response. Every issuance failed at the first authorization with "Authorization offers no http-01 challenge". The locator now tolerates any whitespace and checks that the string is genuinely a type key's value, and the real CA response shape is pinned by self-tests. Failure messages now name the domain they concern, and the no-challenge refusal includes the CA's actual response. Log lines going missing (GitHub issue 33) With Keep log files open enabled, each line sat in a ~4 KB write buffer until later lines pushed it out. On a quiet server the tail of a session stayed invisible; the reporter measured forty minutes. The logger now hands every line to the operating system as it is written. Installations without the setting were never affected. Microsoft 365 Microsoft shuts off Basic authentication for SMTP relay in December 2026. XOAUTH2 bearer login is implemented for outbound relay and for POP3 collection from external accounts. Tokens use the client-credentials flow and are cached to 80% of their lifetime. Bearer auth applies only to destinations on the configured OAuth host list; unlisted relays keep password login unchanged. POP3 collection has no password fallback, deliberately. Sieve and IMAP Sieve now implements variables (RFC 5229), editheader (5293), duplicate (7352), reject/ereject (5429), include (6609), enotify (5435), date/currentdate (5260), spamtest (5235), mailboxexists and :regex. ManageSieve gains RENAMESCRIPT and machine-readable response codes. Eleven IMAP extensions, including APPENDLIMIT (7889), LITERAL- (7888), LIST-STATUS (5819), UNAUTHENTICATE (8437), QUOTA=RES-STORAGE (9208), PREVIEW (8970), MULTIAPPEND (3502), REPLACE (8508), SAVEDATE (8514, schema 6013) and METADATA (5464, schema 6014). The delivery client now opens with EHLO on every delivery, not just routes needing TLS or authentication, and declares SIZE (RFC 1870). Still unimplemented: BINARYMIME, IMAP BINARY, CATENATE/URLAUTH, COMPRESS=DEFLATE, OBJECTID and outbound PIPELINING/CHUNKING. Equal-preference MX records are still not randomised (RFC 5321 5.1). Full release notes, checksums and signatures

This was a beta build of the 6.0 line. 6.0.0 was the production release. Nothing here should be installed today. Build 3 shipped VC++ runtime DLLs that did not match the toolset the binaries were built with, and the service crashed at startup on fresh installs. This build corrects the installer payload. The detail: hMailServer.exe is built with v145 (14.51), but build 3 bundled VS2019-era (14.25) VC++ runtime DLLs app-local in Bin\. Those app-local copies were loaded instead of the system runtimes, and the service died at startup with 0xC0000005 in msvcp140!mtx_do_lock, reached via boost regex and std::mutex. Fresh installs were the ones affected. Changes in this build: The installer now ships Microsoft.VC145.CRT (14.51.36231), matching the build toolset. The stale Microsoft.VC142.CRT payload has been removed. The bundled 2015-era UCRT has been removed. It has been in-box since Server 2016 and Windows 10. build/run-tests.ps1: fixed a stdout/stderr pipe deadlock in the test runner. The full regression gate ran against MariaDB on the MYSQL backend: 898 of 898 passed. Full release notes, checksums and signatures

This was a beta build of the 6.0 line. 6.0.0 was the production release. Nothing here should be installed today. 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. Full release notes, checksums and signatures