Dovecot

Dovecot is a high-performance IMAP and POP3 server used to provide mailbox access for email users and clients. It is widely deployed with MTAs such as Postfix or Exim and supports common mailbox formats and authentication backends.

Key Features

• IMAP4rev1 and POP3 server with TLS/SSL support
• High-performance mailbox index/cache architecture for fast access
• Supports Maildir and mbox (and can integrate with other storage via plugins)
• Authentication framework with multiple backends (e.g., PAM, LDAP, SQL) and pluggable mechanisms
• SASL integration commonly used by Postfix for SMTP authentication
• Quota and ACL support (IMAP ACL) for shared mailboxes and access control
• Sieve mail filtering via Pigeonhole (separate but commonly paired component)
• Replication and high-availability options (dsync-based replication)

Use Cases

• Provide IMAP/POP3 access for a self-managed email domain (paired with Postfix/Exim)
• Centralized authentication for mail services (LDAP/SQL/PAM) with per-user mail storage
• Shared mailboxes and delegated access scenarios (teams/support mailboxes)

Limitations and Considerations

• Not a full email stack by itself: you typically pair it with an MTA (e.g., Postfix) and optional anti-spam/AV components
• Some advanced functionality (e.g., Sieve filtering) is delivered via companion projects/plugins (not strictly in the core daemon)

Dovecot is a mature, widely used mailbox-access server emphasizing speed, interoperability, and flexible authentication/storage integrations. It fits well in production mail setups where IMAP/POP3 reliability and performance are critical components.