Features

• Added DMARC support: incoming messages can now be checked against the sender domain's DMARC policy.
• Passwords are now stored using Argon2id or PBKDF2, selectable by the administrator.
• Delivery status notifications (bounces) now include In-Reply-To and References headers, so mail clients thread them together with the original message.
• The IMAP OnClientLogon event is now fired for clients logging on with AUTHENTICATE PLAIN, not just LOGIN.

Bug fixes

• Backup and restore now compress and decompress using half of the available processor cores instead of all available.
• The bundled 7-Zip used for backup and restore was upgraded to 26.03.
• Fixed: several issues with concurrent access to the same IMAP mailbox from multiple clients.
• Fixed: an external POP3 fetch account could stay locked after a failed fetch, silently stopping mail collection for that account until the server was restarted.
• Fixed: a failed DNS lookup was treated as "no records found", which could cause a message to be scored as spam when the HELO host could not be looked up
• Fixed: the data directory synchronizer could have deleted live message files in public folders when run in delete mode.
• Fixed: a client could bypass the required HELO/EHLO greeting by sending RSET, or by sending MAIL FROM directly after a STARTTLS handshake

Installation

• New installations now run the hMailServer service as Network Service, with data and logs stored in C:\ProgramData\hMailServer
• Fixed: the installer overwrote the ValidLanguages setting, discarding any changes the administrator had made to it.

Installation

• Bundle libmariadb.dll with the installation (#479)
• Support for passing in the password during install (#570)
• Installer now propagates a non-zero exit code when DBSetup fails

Stability fixes

• Addressed race conditions during IMAP communication
• Fixed a file received over SMTP being left open
• Fixed memory leak when reloading and checking event scripts
• Upgraded to OpenSSL 3.5.8

Other

• Documentation refresh

• Experimental support for MariaDB Connector (C). To use, put libmariadb.dll in hMailServer\Bin. hMailServer will prefer it over libmysql.dll if both exists.
• IMAP improvements
  • Removed the ImapAuthAllowPlainText legacy option
  • Fixed invalid "Recent" count in IMAP notifications
  • Fixed FETCH not honoring the start.size partial-fetch clause
• DKIM improvements
  • DKIM signatures for domain aliases
  • DKIM-sign all email sent from a domain, not just per-account
  • Fixed signing failure for messages >10MB
  • DKIM verification when the published DNS record is a CNAME
  • Signing for NDR/bounce messages
• Optional X-Original-Rcpt-To header for incoming mail.
• IMAP improvements: RFC 6154 support - LIST extension for Special-Use Mailboxes (\Sent, \Drafts, \Junk, \Trash, etc.), including auto-creation of special-use folders on account creation.
• Security: TLS 1.3 support added
• Security: OpenSSL upgraded to 3.5.7
• 64-bit only. Support for x86/32-bit dropped.