Dovecot IMAP and POP3 Server

Dovecot is an open-source IMAP and POP3 email server for Linux and UNIX-like systems, designed with a primary focus on security, reliability, and performance. Created by Timo Sirainen in 2002, Dovecot has become the most widely deployed open-source IMAP server, powering email for major hosting providers, universities, and enterprises including cPanel installations on millions of servers. Key features include: IMAP and POP3 support (full IMAP4rev1 and POP3 protocol compliance with IDLE for push email, CONDSTORE and QRESYNC for fast mailbox synchronization, and SORT and THREAD for server-side message sorting), high performance (optimized for both small and large mailboxes with index file caching, lazy mailbox synchronization, and efficient disk I/O patterns), security (mandatory TLS/SSL, Kerberos/GSSAPI authentication, challenge-response authentication via SCRAM-SHA, and multiple authentication backends including PAM, LDAP, SQL, passwd, and vpopmail), maildir and mbox formats (and the high-performance mdbox and sdbox formats for deduplicated storage with compression), high availability (Dovecot Director for horizontal scaling and load balancing across backend mailbox servers, replication for real-time mailbox synchronization between servers), full-text search (dovecot-solr, dovecot-ftl, and built-in FTS for indexing message content for fast keyword search), quota support (per-user, per-domain, and per-mailbox quota enforcement), Sieve filtering (Pigeonhole Sieve plugin for server-side email filtering, vacation auto-replies, and message redirects), shared mailboxes (ACL-based sharing of mailboxes between users), plugins (push notification, antispam integration, lazy plugexpunge, and last-login tracking), and clustering (dsync replication and failover for multi-server deployments).