Seven years after the release of version 2.3.0, a new branch of the multi-platform IMAP server Dovecot 2.4.0 is presented, supporting the POP3 and IMAP4rev1 protocols with popular extensions such as SORT, THREAD, MULTIAPPEND, QUOTA, ACL, COMPRESS, NOTIFY, METADATA, and IDLE, along with authentication and encryption mechanisms (SASL, TLS, SCRAM, XOAUTH2). Dovecot maintains full compatibility with classic mbox and Maildir by applying external indexes to enhance performance. Plugins can be used to extend functionality, providing features such as quotas, ACLs, push notifications, full-text search, and virtual mailboxes. The project's code is distributed under the LGPL and MIT licenses.
Key Changes:
- Changes have been made that break backward compatibility with the configuration used for the 2.3.x branch. For example, a new variable expansion syntax has been introduced (‘%{local_port}’ instead of ‘%a’ etc.) and modifiers (‘%{user | md5 | hexlify(1)}’ instead of ‘%1Mu’ etc.), the specification of a name in the passdb and userdb sections is now mandatory, many settings have been renamed, and quota settings have been moved to a separate section.
- Experimental support for the SMTPUTF8 extension (RFC 6531) and the ‘IMAP UTF8=ACCEPT’ mode has been added, allowing the use of national alphabet characters in email addresses, host names, mailbox names, and headers. To enable this, a build with the ‘--enable-experimental-mail-utf8’ option is required when invoking the configure script, and the setting ‘mail_utf8_extensions=yes’ must be applied.
- Support for the ARGON2 password hashing scheme, SASL algorithms SCRAM-SHA-1 and SCRAM-SHA-256, and elliptic curves X25519 and X448 has been added.
- The LDAP authentication driver now supports attributes that include multiple values (multi-value).
- Support for TLS Channel Bindings extension has been added.
- During authentication, the implementation now tracks JA3 hashes, which allow the identification of the software used to establish the connection based on connection parameter characteristics.
- A new full-text search plugin fts-flatcurve has been added, utilizing the Xapian engine.
- In IMAP, support for the INPROGRESS return code (RFC 9585) has been added, which can be used to send notifications about the progress of long-running operations.
- A DNS client and HTTP client have been implemented in lib-lua.
- SCRAM-SHA mechanisms have been added to lib-sasl.
- Support for SNI (Server Name Indication) has been added to LMTP, allowing settings to be bound to the name server, the information about which is transmitted openly during the TLS session.
- Support for Write-Ahead Logging (WAL) mode has been added to the SQLite driver.
- Automatic activation of the IMAP extension COMPRESS has been provided for compressing data transmitted through the connection to the IMAP server.
- The parameter auth_internal_failure_delay has been added, which defines the delay before sending a response to the client in case of an authentication error due to an internal failure.
- The parameter fts_message_max_size has been added, which sets the maximum size of the email body that can be indexed by the full-text search engine.
- The parameter login_socket_path has been added, specifying the path to the socket used by login processes.
- The parameter quota_mailbox_count has been added, which sets the maximum number of mailboxes that can be created.
- The parameter quota_mailbox_message_count has been added, which sets the maximum number of messages allowed in a single mailbox.
- The parameter submission_add_received_header has been added, controlling the addition of the 'Received:' header to emails (which can be used to hide sender information).
- The cassandra_log_retries parameter has been added to control the logged information about failures during retries for Apache Cassandra.
- The acl_global_path setting has been deprecated (support for global files and directories with ACL has been discontinued).
- Support for full-text indexers fts-lucene and fts-squat has been discontinued (moved to plugins), the dsync utility has been replaced with doveadm sync, the IMAP SETQUOTA command and set_quota settings, Dovecot Director and replicator architecture (NFS is recommended instead), and Sieve extensions notify, imapflags, and vnd.dovecot.duplicate have been removed.
- The Lua Authentication Database has replaced the databases checkpassword, passdb, and userdb for authentication data.
- Support for the plugins zlib, listescape, old-stats, and mailbox-alias has been discontinued.
- Support for the Memcached driver has been discontinued, with the Redis driver recommended instead.
- Support for the shadow driver has been discontinued, with the PAM-based authentication database recommended instead.
- Support for Berkeley DB in dict_db_config has been discontinued.
- Support for unreliable password hashing schemes is disabled by default (to re-enable, use the auth_allow_weak_schemes parameter).
- Support for OpenSSL versions before 1.0.2 has been discontinued.
Source: opennet.ru
