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.