hMailServer FAQ

Yes, hMailServer is still maintained. Progressive Robot Ltd forked it in 2026 and maintains the hMailServer 6 line. The current release is hMailServer 6.3.8, a security release published on 2 November 2026 for Windows and for Linux on x86-64 and AArch64. 6.3.6, of 6 October 2026, was the last release planned by date; the releases since, 6.3.7 and 6.3.8, are security releases cut from master, and the 6.3 line receives security fixes until 30 September 2027.

Martin Knafve created hMailServer. The original project went quiet for years. In 2026 Progressive Robot forked it, rebuilt it on a current toolchain (Visual Studio 2026 and OpenSSL 4, 64-bit only) and released hMailServer 6.0.0 on 12 June 2026. Linux support arrived in hMailServer 6.3.0 on 10 September 2026; 6.3.8 is packaged for x86-64 and AArch64, with a package for each of nine distribution releases beside the generic .deb and .rpm, and a container image. The original project has since resumed development as well. Its changes are reviewed against the hMailServer 6 code, and several have been ported.

Release notes, SHA-256 checksums and packages for every version are on the downloads page. New releases are announced in Announcements & releases.

Progressive Robot Ltd, based at Chester Business Park in Chester, United Kingdom, forked hMailServer in 2026 and maintains the hMailServer 6 line. hMailServer was originally created by Martin Knafve, and the original project has since resumed development independently of this fork.

Progressive Robot has published hMailServer 6 releases since 6.0.0 on 12 June 2026; the current release is hMailServer 6.3.8, released 2 November 2026. Since 6.3.1 the Windows installer has carried an Authenticode signature naming Progressive Robot Ltd, and the 6.3.2 release notes state that the project's GOVERNANCE.md names two maintainers.

Progressive Robot also runs this forum, where its staff post as chris and Progressiverobot. hMailServer remains free and open source under AGPL-3.0, with no per-mailbox fees and no paid tiers. See About this forum, the official hMailServer page and the GitLab repository.

hMailServer was originally created by Martin Knafve. The readme of hMailServer 6.0.0 Beta 1, dated 12 June 2026, credits the software as "Based on hMailServer by Martin Knafve". Under the original project it was a free, Windows-only mail server from 2002.

Progressive Robot did not create hMailServer. It forked the original project in 2026, after that project had gone quiet for years, and maintains the hMailServer 6 line. The first production release, hMailServer 6.0.0, is dated 12 June 2026, and hMailServer 6.3.0 added Linux support on 10 September 2026. The original project has since resumed development. The notes for the hMailServer 6.2.23-alpha2 pre-release of 4 September 2026 record that seven fixes were taken from it. See About this forum.

hMailServer is free and open source under the AGPL-3.0 licence, including for commercial use, with no per-mailbox fees and no paid tiers. The current release is hMailServer 6.3.8, released on 2 November 2026. It is a free download for Windows (x64, and a preview for ARM64) and for Linux on x86-64 and AArch64, and as a container image. Simply using hMailServer requires nothing of you under the licence. If you modify it and offer it to others over a network, you must publish your changes.

The Windows installer and the Linux .deb and .rpm packages are on the official downloads page, and the source code is on GitLab, with the source and every release mirrored on GitHub since 18 October 2026. Progressive Robot Ltd, which maintains the hMailServer 6 line, sells optional managed hMailServer services and support plans. No answer on this forum is gated behind a support plan.

hMailServer 6.3.8 is the latest release of hMailServer, published on 2 November 2026 for Windows and Linux under the AGPL-3.0 licence. It is a security release: 6.3.6, of 6 October 2026, was the last release planned by date, and the releases since, 6.3.7 and 6.3.8, are security releases cut from master; the 6.3 line receives security fixes until 30 September 2027. It ships as an x64 Windows installer, hMailServer-6.3.8-x64.exe, a preview installer for Windows on ARM64, a .deb and an .rpm for x86-64 and AArch64 Linux with a package for each of nine distribution releases beside the generic ones, two AppImages, a Helm chart and a container image, registry.gitlab.com/hmailserver/hmailserver:6.3.8, each file signed with Sigstore by the project's GitLab pipeline.

Every server running 6.3.7 or earlier should upgrade. hMailServer 6.3.8 fixes vulnerabilities the project found in its own code, reaching back to 6.0.0's first beta, each with a CVE requested. Among the fixes, the auto-ban saves the IP range it adds under a name of its own, so that it bans the address; the CardDAV, CalDAV and Autodiscover listener refuses an address an auto-ban or an IP range bans; TlsMode=verify-full on MySQL and MariaDB checks the database server's certificate against the CA file TlsCaFile names; and on Windows setup makes or hardens the program folder before it copies a file or runs a program of the installation, and refuses one that another account controls, the four narrower cases of work item 78 that 6.3.7's notes left open. Its Helm chart starts a server, which those of 6.3.6 and 6.3.7 did not, its container image reaches a MariaDB database, and its Windows installer refuses the original hMailServer's 5.7.

The schema stays at 6108: from 6.3.6 or 6.3.7 the upgrade changes no table, and from 6.3.5 or older it still runs 6.3.6's three one-way steps, so back up the database and the data directory first. On 6.3.6 or 6.3.7 the live update installs it; on 6.3.4 or 6.3.5 it does for a Windows service running as LocalSystem, and other servers there upgrade by hand or with apt, dnf or zypper; a server from 6.2.28 to 6.3.3, or from 6.3.3's AArch64 packages or AppImages, upgrades by hand, once. The exceptions, and what changes on upgrade, are under "Upgrading" and "Before you upgrade" in the 6.3.8 announcement. See the release notes, the mirror on GitHub and Announcements & releases.

Yes, hMailServer 5.3, 5.4, 5.5 and 5.6 installations on Windows upgrade in place directly to hMailServer 6.3.8, released on 2 November 2026, with no intermediate versions; the original hMailServer's 5.7 releases do not. Run hMailServer-6.3.8-x64.exe as administrator and accept the upgrade. The installer upgrades the database schema to 6108 and keeps mail, accounts, domains and settings.

The original project's 5.7 releases (5.7.0 and its pre-release builds 2788 and 2843, 5.7.1 and 5.7.2) took its schema to 5709 to 5711, which this fork's upgrade chain has no step from: 6.3.8's installer refuses such an installation before it changes anything, and the installers of 6.3.7 and earlier, which do not look, must never be run over one. Move such a server's mail over IMAP instead, as Migration.md says under "From the original hMailServer".

The schema upgrade is one-way, so back up the database, the data directory and hMailServer.INI first, and on 5.3 to 5.5 also test the restore. On a large database, plan a maintenance window for four of the schema steps. On MySQL or MariaDB the upgrade needs MySQL 5.7.9 or MariaDB 10.2.2 or later and the ALTER privilege, or it stops at step 6041 having changed nothing. Change hMailServer.INI after the upgrade, not before: since 6.3.4 the database holds the settings. Since 6.3.6 the installer makes the data, log, database and event folders private to the administrators and the service, so a backup program or a script that read them as an ordinary account needs an entry of its own. Since 6.3.7 it also hardens the program folder, and 6.3.8's setup refuses one that another account controls (exit code 7); for an installation at the root of a drive, read "Before you upgrade" in the 6.3.7 and 6.3.8 announcements first.

The classic Administrator (hMailAdmin.exe) is replaced by the Control Panel (hMailCP.exe), and the PHP WebAdmin is gone. If the installer cannot add the .NET 10 Desktop Runtime, the schema is not upgraded and the service will not start: install the runtime by hand, then run DBUpdater.exe. See chapter 18 of the hMailServer documentation or ask in Installation, migration & upgrades.

To verify an hMailServer 6.3.8 download (the current release, 2 November 2026), check the Sigstore bundle that sits beside every file of the release as <file>.cosign.bundle. With cosign, run cosign verify-blob --bundle hMailServer-6.3.8-x64.exe.cosign.bundle --certificate-identity 'https://gitlab.com/hmailserver/hmailserver//.gitlab-ci.yml@refs/tags/v6.3.8' --certificate-oidc-issuer https://gitlab.com hMailServer-6.3.8-x64.exe, which must say Verified OK. The identity is the project's GitLab pipeline for the release's tag, and the certificate carries the project's id, 86730559, which cosign does not check: the release notes give the OpenSSL command that reads it. 6.3.5's files name Progressiverobot/hmailserver, the path the project had before 29 September 2026. Then sha256sum --ignore-missing -c hmailserver-linux-6.3.8-SHA256SUMS.txt must say OK for each Linux file, and on Windows Get-AuthenticodeSignature .\hMailServer-6.3.8-x64.exe must answer Valid, signed by Progressive Robot Ltd; the x64 installer's published SHA-256 is 4b9b9c3102cbed743f6c826289c54cec25c395d02208e55cdd3219187fbf8654. On Linux a server from 6.3.4 on makes the same check as its live update with hmailserver --verify-update <file>. hmailserver-6.3.8.intoto.sigstore.json is the release's SLSA v1 build provenance, which names every file by its SHA-256; new in 6.3.8, hmailserver-6.3.8.intoto.jsonl is its signed envelope alone, as one line of JSON, without the certificate, so the bundle is still the file to verify with. The files on the GitHub mirror are the same files and verify the same way, except that GitHub names the Debian and Ubuntu per-release packages with a dot where the checksum list has a tilde (hmailserver_6.3.8-1.debian12_amd64.deb for hmailserver_6.3.8-1~debian12_amd64.deb): rename such a file before sha256sum -c, or compare its hash by hand.

The releases from 6.2.19 to 6.3.3 carry Sigstore bundles signed by the project's former GitHub workflow, and 6.3.4 alone has none: its checksum list is signed with the SSH key that signs the release tags. See "Verifying a release" in SECURITY.md, the 6.3.8 release and the downloads page, which shows each file's SHA-256.

hMailServer has run on 64-bit Linux since hMailServer 6.3.0, released on 10 September 2026. The current release, hMailServer 6.3.8 of 2 November 2026, ships for x86-64 and AArch64: a generic .deb and .rpm, and a package of its own for each of Debian 12 and 13, Ubuntu 24.04, Fedora 43 and 44, Enterprise Linux 9 and 10, and openSUSE Leap 16.0 and Tumbleweed, each built and tested in that release's own container (the AArch64 ones under emulation). Each installs a systemd service configured under /etc/hmailserver. The generic .deb does not install on Debian 12, nor the generic .rpm on Enterprise Linux 9: each takes its own release's package. There are also two AppImages, a container image, registry.gitlab.com/hmailserver/hmailserver:6.3.8, for linux/amd64 and linux/arm64, which since 6.3.8 also reaches a MariaDB database, and a Helm chart, which since 6.3.8 starts a server, as the charts of 6.3.6 and 6.3.7 did not. 6.3.8 adds an Ansible collection, a Kubernetes operator for Operator Lifecycle Manager and a container on Proxmox VE. The collection is not yet on Ansible Galaxy, and the one in the source tree installs 6.3.7 unless it is given another release's SHA-256; the Proxmox VE scripts have not yet run on a Proxmox VE host. Arch uses the PKGBUILD in the source tree. The database is PostgreSQL or MySQL/MariaDB.

Linux has no Control Panel, COM API or Microsoft SQL Server support. A Linux server is administered through the hmailserver command line, the REST API and the browser Control Deck, which is also where per-domain DKIM is configured. Since 6.3.4, event scripts run on Linux in JavaScript. Since 6.3.8 the server names files in UTF-8 whatever LANG says, so on a server that ran under a LANG that is not UTF-8, with files or folders named outside ASCII, rename each to its UTF-8 name before upgrading. Moving an existing Windows installation to Linux is not a supported migration. See Running hMailServer on Linux and the Linux category.

hMailServer 6.3.8, released on 2 November 2026, supports Windows 10 version 1607 or later, Windows 11, and Windows Server 2016 or newer, on 64-bit x64 systems. The Windows download is a single installer, hMailServer-6.3.8-x64.exe, and there has been no 32-bit build since hMailServer 6.0. A second installer, hMailServer-6.3.8-arm64.exe, is a preview for Windows on ARM: it is cross-compiled and has never run on ARM64 hardware, and a new ARM64 installation needs SQL Server or PostgreSQL, since SQL Server Compact has no ARM64 build. The documentation asks for at least 2 GB of RAM and 20 GB of free disk space.

Run the installer as an administrator. It upgrades an existing hMailServer 5.3 to 5.6, 6.0, 6.1, 6.2 or 6.3 installation in place, and refuses an installation of the original hMailServer's 5.7 releases before it changes anything; a server on 6.3.6 or 6.3.7 can install it by the live update instead, as can one on 6.3.4 or 6.3.5 whose service runs as LocalSystem. Since 6.3.8 setup refuses, with exit code 7, a program folder that an account other than SYSTEM, the Administrators and TrustedInstaller controls, and names the icacls command that deals with it. The Control Panel and the database tools are .NET 10 applications, and the installer adds the .NET 10 Desktop Runtime if it is missing, but does not replace one already installed: keep that up to date through Microsoft Update. Windows is the more complete platform: the Control Panel, the COM API and VBScript or JScript event scripts are Windows-only, while Linux runs event scripts in JavaScript and configures per-domain DKIM over the REST API. See chapter 3, "Before you install: the checklist", in the hMailServer documentation, and Installation, migration & upgrades.

hMailServer supports four databases on Windows: the built-in SQL Server Compact database (the default), MySQL or MariaDB, Microsoft SQL Server (including the Express edition) and PostgreSQL. On Linux, supported since hMailServer 6.3.0 (10 September 2026) and in the current release, 6.3.8 (2 November 2026), it supports two: PostgreSQL and MySQL/MariaDB. Upgrading to hMailServer 6.3.4 or later on MySQL or MariaDB needs MySQL 5.7.9 or MariaDB 10.2.2 or later and the ALTER privilege, and since 6.3.4 the server connects to them over TLS whenever the database server offers it. Since 6.3.7 the x64 Windows installer carries MariaDB Connector/C 3.4.11, with seven authentication plugins where 6.3.6's had nine: a database account that signs in with MySQL Enterprise's Windows authentication can no longer do so. Since 6.3.8 that client loads its plugins only from the installation's own plugin folder, and TlsMode=verify-full on MySQL and MariaDB checks the database server's certificate against the CA file TlsCaFile names; a verify-full connection through MariaDB Connector/C to a database server on the same machine without TlsCaFile is refused with HM7535, so name in TlsCaFile a CA that issues nothing but the database's certificates, the one that issued its certificate, or set TlsMode=require, before upgrading.

The Linux build refuses Microsoft SQL Server and SQL Server Compact by name, with an explanation in the error log, because both are reached through Windows-only interfaces. It was tested end to end against PostgreSQL 18 and MariaDB 11.8. PostgreSQL is reached through libpq, which the package depends on. The MySQL/MariaDB client is loaded at run time and must be installed separately: libmariadb3 on Debian and Ubuntu, mariadb-connector-c on Fedora and RHEL, mariadb-libs on Arch. It should be MariaDB Connector/C 3.4.11 or later; where it is older and not patched, name the CA in TlsCaFile. Since 6.3.8 the container image carries it too.

The documentation calls the built-in database adequate on Windows for up to a few dozen mailboxes, and lists MySQL/MariaDB for most production use and PostgreSQL for larger installations. See choosing a database and creating the database on Linux.

Moving an hMailServer installation from Windows to Linux is not a supported migration in hMailServer 6.3.8, released 2 November 2026. Both platforms use database schema 6108 and the same message store format, but there is no tested path, so the documentation says to treat the move as a new installation plus a mailbox-level migration, not as a restore.

Known breaks:

• A configuration file with Type=MSSQL or Type=MSSQLCE is refused on Linux; migrate that database to PostgreSQL or MySQL on Windows first.
• DPAPI-protected secrets, including route, fetch-account and relay passwords, private-key passphrases and the administrator's TOTP secret, cannot be read on Linux and must be re-entered.
• COM integrations do not work on Linux, and event scripts run there in JavaScript only, so a VBScript or JScript file has to be ported.
• Per-domain DKIM key files hold Windows paths: copy the keys and point each signing domain at them again.
• Directory names derived from addresses are lower-cased, and the message store must be owned by hmailserver.

If you try anyway, keep the Windows server running until the copy is verified. See section 35.14 of the hMailServer documentation, or ask in Installation, migration & upgrades or Linux.

hMailServer has a built-in webmail at /portal, served by its REST API listener and compiled into the server binary on both Windows and Linux. A browser mailbox page arrived in hMailServer 6.2.28, it became a full webmail in 6.3.0, and hMailServer 6.3.3 rebuilt it in the shape of Gmail and Outlook.com; hMailServer 6.3.4 added calendars, contact groups, the organisation's directory and passkey sign-in; the current release is 6.3.8 (2 November 2026).

It is off by default. Setting RestApiPort turns on the REST API, the Control Deck and the webmail together: in the Control Panel on Windows, or with sudo hmailserver --set-setting RestApiPort=<port> on Linux. Since 6.3.4 the database holds the settings, so a line edited in hMailServer.ini after the first start is put back. The listener will not start while the administrator password is empty, binds to 127.0.0.1 by default, and needs a TLS certificate and key before it can bind to a non-loopback address. Users sign in with their own mailbox address and password; the administrator password and API keys are refused. IMAP clients, or Roundcube pointed at the IMAP service, remain a reasonable alternative. See chapter 36, the version history and Webmail, portal & Control Deck.

hMailServer supports Let's Encrypt through a built-in ACME v2 client that obtains a certificate, assigns it to TLS ports that have none of their own and renews it before expiry, with no scheduled task or manual restart. Use hMailServer 6.2.25 or later on Windows, or 6.3.0 or later on Linux; the current release is 6.3.8 (2 November 2026). Since 6.3.7 the HTTP-01 challenge responder serves up to 64 connections at once; earlier versions served one at a time, so idle clients could make issuance or renewal fail. Releases up to 6.2.21 never obtained a certificate from Let's Encrypt, and 6.2.24 stopped the service whenever a certificate was issued or renewed.

The client is off by default. Set AcmeEnabled=1, AcmeContactEmail and AcmeDomains in the Control Panel under Settings, Security, Certificates (ACME), over the REST API, or on Linux with sudo hmailserver --set-setting. Since 6.3.4 these are database settings: a line edited in hMailServer.INI after the first start is put back. Since 6.3.8 a certificate that does not name every host in AcmeDomains is due at once, where an added host waited for the renewal, and GET /api/v1/acme, POST /api/v1/acme/run and the Control Deck's Certificates page show the certificate's state and ask for a check, within the CA's rate limits.

Validation uses HTTP-01, so port 80 must be reachable from the internet and every name in AcmeDomains must already resolve to the server. Keep AcmeReuseKey=1 (the default) so published DANE TLSA records stay valid across renewals. Where AcmeDomains lists a host the certificate lacks, the first check after an upgrade to 6.3.8 orders a certificate for every host on the list, and a host the CA cannot validate fails the whole order and holds the renewal for the others: take such a host off the list first. See the hMailServer documentation (sections 9.1 and 35.9) and TLS, certificates & deliverability.

hMailServer supports SPF, DKIM, DMARC, MTA-STS and DANE, plus ARC sealing and TLS-RPT. MTA-STS, DANE, DMARC, ARC, TLS-RPT and Ed25519 DKIM arrived in hMailServer 6.0.0.

For outbound mail, MtaStsEnabled, DaneEnforcementEnabled and DnssecValidationEnabled are on by default. If a recipient domain has published a policy, it must present verified TLS or the message is deferred rather than sent unencrypted. To host your own MTA-STS policy, turn on the web-services listener with WebServicesHttpsPort=443.

hMailServer signs outgoing mail with RSA or Ed25519 DKIM keys, and scores inbound SPF, DKIM and DMARC failures as spam tests. You still publish your own SPF, DKIM and DMARC records in DNS.

Caveats: ARC sealing is off by default and seals only mail from hosted, DKIM-enabled domains. TLS-RPT reports are sent only once TlsRptFromAddress is set. On Linux, per-domain DKIM signing is configured over the REST API or on the Control Deck. Since 6.3.7 an authenticated submission is signed as a hosted domain only when its account may send as the From address, and mail from outside whose From names a hosted domain is no longer signed with that domain's key (CVE-2026-107567). Since 6.3.4 a domain's DKIM keys can also rotate on a policy, off by default, and SPF follows RFC 7208, so mail from 127.0.0.1 or ::1 no longer passes it unconditionally.

See the hMailServer documentation (chapters 8 and 9) and TLS, certificates & deliverability.

hMailServer has had a REST API since version 6.0.0, served under /api/v1/ and described by an OpenAPI 3.0.3 document at GET /api/v1/openapi.json. It gained a large write surface in 6.3.0 (10 September 2026). At hMailServer 6.3.4 the project's parity check counted 458 of the 466 properties the Windows Control Panel writes as writable over REST; the eight it lists as missing, an account's directory fields, are written on a route of their own.

The API is off by default on Windows and Linux. Setting RestApiPort turns it on, bound to 127.0.0.1 by default: in the Control Panel, over COM, or on Linux with sudo hmailserver --set-setting RestApiPort=<port>. Since 6.3.4 the database holds these settings, not hMailServer.ini. It will not start with an empty administrator password, and on any address other than 127.0.0.1, localhost or ::1 it needs a TLS certificate and key. Credentials are the administrator password, scoped API keys, session cookies and a mailbox's own login, which reaches only /api/v1/me and sign-in. Linux has no Control Panel or COM, so there the REST API and the Control Deck it serves at / do that job. Since 6.3.8 a request body meant to be JSON must be one JSON object: the server answers 400, saying why, to one that is not, that names a member twice, holds an escaped U+0000 or passes the bounds of 100,000 values and 32 levels deep. See the REST API chapter and REST API & integrations.

hMailServer is not a replacement for Microsoft Exchange: it is a mail server for SMTP, IMAP and POP3, with no Teams integration and no ActiveSync. The current release, hMailServer 6.3.8 (2 November 2026), is free and open source under the AGPL-3.0 licence, with no per-mailbox fees, and runs on Windows and Linux.

It hosts mail for many domains, with spam filtering, virus scanning through ClamAV, a rules engine and Sieve filtering. It serves each account's address book over CardDAV (since 6.3.3) and, since 6.3.4, calendars over CalDAV, with invitations, free-busy, delegation and bookable rooms, once the web services HTTPS listener is turned on.

Users read mail in Outlook, Thunderbird, Apple Mail, on a phone or in the built-in webmail at /portal once the REST listener is turned on. The documentation suggests it for small businesses, developers needing a real SMTP and IMAP test endpoint and hosting providers. If nobody on staff is comfortable editing DNS records and watching a log file, it says a hosted mailbox provider will serve them better. See chapter 1 of the hMailServer documentation.

Free help with hMailServer is available on the hMailServer community forum, run by Progressive Robot Ltd, which forked hMailServer in 2026 and maintains the hMailServer 6 line. hMailServer is free under AGPL-3.0, and no answer on the forum is gated behind a support plan.

Post general problems in General support; Linux, TLS, certificates & deliverability and REST API & integrations have their own categories. Follow the how to ask template: the full version with its build stamp, the platform, the database, how the install got there, and a log excerpt with timestamps intact and credentials redacted.

The hMailServer documentation runs to 37 chapters. Reproducible defects go on the GitLab issue tracker, linked from the forum thread. Without a GitLab account, email the defect, or a question for the maintainers, to the project's Service Desk address, contact-project+hmailserver-hmailserver-86730559-issue-@incoming.gitlab.com: GitLab files the message as a confidential issue, which only the maintainers see, and their replies reach you by email. Never post security vulnerabilities publicly: report them privately by one of the two routes in SECURITY.md, a confidential GitLab issue or an email to the project's Service Desk address.

For paid help, Progressive Robot offers deployment, migration, hardening and fully managed hMailServer on Windows and Linux. See support plans, Managed hMailServer or contact Progressive Robot.

Report a security vulnerability in hMailServer privately, never in a forum thread or a public GitLab issue. There are two routes, and both reach the maintainers as a confidential issue: open a confidential issue on GitLab with the Security template, checking that This issue is confidential is still ticked, or email the project's Service Desk address, contact-project+hmailserver-hmailserver-86730559-issue-@incoming.gitlab.com, which needs no GitLab account. Include the hMailServer version, the platform, the database and enough detail to reproduce the problem.

The maintainers aim to acknowledge a report within 5 working days and to ship a fix for a confirmed vulnerability within 90 days, and the release notes credit you unless you would rather not be named. Security advisories are posted in Announcements & releases. The full policy is in SECURITY.md, and this is rule 6 of the forum rules.

The hMailServer 6 source code is on GitLab at gitlab.com/hmailserver/hmailserver, under the AGPL-3.0 licence. Progressive Robot Ltd forked hMailServer in 2026 and maintains the hMailServer 6 line in that repository. The original project, created by Martin Knafve, is separate and has resumed development. Since 18 October 2026 the source and every release are also mirrored on GitHub at github.com/RainbowWizard-coder/hMailServer; issues are off there, and issues and merge requests stay on GitLab.

One source tree builds the 64-bit Windows server with Visual Studio 2026 and MSVC. Since hMailServer 6.3.0 it also builds the Linux server with clang or GCC. Every release from 6.0.0 to the current 6.3.8 has a tag. Since 6.2.24, two clean builds of each release have produced a byte-identical hMailServer.exe, so anyone with the same toolchain can rebuild a tag and compare the result. The Linux build steps are in supported platforms and packages. Reproducible defects go on the GitLab issue tracker, or, without a GitLab account, by email to the project's Service Desk address, contact-project+hmailserver-hmailserver-86730559-issue-@incoming.gitlab.com, which GitLab files as a confidential issue that only the maintainers see.

No. The hMailServer community forum at www.hmailserver.co.uk is separate from the forum at hmailserver.com, which belongs to the original hMailServer project created by Martin Knafve. This forum is run by Progressive Robot Ltd, which forked hMailServer in 2026 and maintains the hMailServer 6 line. The current release is hMailServer 6.3.8, released on 2 November 2026 for Windows and Linux under the AGPL-3.0 licence.

The original project went quiet for years and has since resumed development separately. Accounts and posts from hmailserver.com were not carried over, so register here to post. Staff post under their own accounts, chris and Progressiverobot.

Release notes, security advisories and forum notices are posted in Announcements & releases. Support questions go in categories such as General support, Installation, migration & upgrades, Linux and TLS, certificates & deliverability. Before posting, read the forum rules and the template on posting a support request.