Since 6.3.0 the same source tree builds, installs and delivers mail on x86-64 and AArch64 Linux, as a systemd service, from a .deb, an .rpm or an Arch PKGBUILD. That is why the release is numbered 6.3 and not 6.2.29. Read §35.1 before you install anything. Finding out about a missing capability after the mailboxes are populated is the wrong order. What crossed The SMTP, POP3 and IMAP engines, delivery, routing, rules, anti-spam, anti-virus, ACME, the backup manager, the REST API, the Control Deck and the self-service portal. The on-disk message format is unchanged: one directory per domain and per mailbox, one file per message. The database schema is the same version the Windows build of the same release needs. The packages A .deb for Debian, Ubuntu and derivatives. An .rpm for Fedora, RHEL and derivatives, which openSUSE also consumes, though not separately exercised in CI. Arch is a PKGBUILD in the tree, built with makepkg -si from the git tag. Both architectures are built natively in CI. Nothing else is packaged. The AppImage is not for running mail. It runs as whoever started it, with no hmailserver user, no unit and none of the systemd hardening, it puts its store under the invoking user's home directory, and it cannot bind port 25. Use it to see the thing work on a laptop. §35.2. Where things live Configuration is /etc/hmailserver/hMailServer.ini at 0640 root:hmailserver. The store is /var/lib/hmailserver, the logs /var/log/hmailserver, the unit /usr/lib/systemd/system/hmailserver.service. The service runs as hmailserver:hmailserver and never as root. Full table: §35.6. The backends are PostgreSQL through libpq, a link-time dependency, and MySQL or MariaDB through a client loaded with dlopen at run time, which nothing pulls in for you. SQL Server and SQL Server Compact are refused by name, so an INI carried across from Windows is repointed or it does not start. The gaps, stated plainly No Control Panel and no COM API. Both are Windows-only and are not compiled here. Every third-party COM script stops at that boundary. No event scripts. There is no script engine, and a non-empty script file is reported as uncompilable. Per-domain DKIM cannot be configured. There is a read route and no write route: a PUT to /api/v1/domains/{domain}/dkim answers 404. A domain that must sign its outbound mail with DKIM is not one to run on this platform today. The same gap takes per-domain size limits, the domain signature and a per-domain relay host with it. No self-update. The update checker names the package your machine would install, and the apply step refuses. You upgrade with apt, dnf or pacman. No tested path from Windows. The schema and the store format are shared, so the pieces are there. Nobody has run a Windows installation onto Linux and verified the result. §35.14 says what is known. Administration is therefore the Control Deck at / on the REST listener, and the REST API behind it. §35.10 covers the daily jobs.