...It bundles the core mail stack—Postfix for SMTP and Dovecot for IMAP/POP3—then layers in optional anti-spam and anti-virus services, DKIM/DMARC signing and verification, and rate-/abuse-protection tooling. The project emphasizes secure defaults while exposing configuration via environment variables and mounted files, allowing you to define users, aliases, domains, and sieve filters without rebuilding images. It integrates smoothly with Let’s Encrypt for TLS, supports LDAP and other auth backends, and ships with scripts to validate DNS records and common misconfigurations. Persistent volumes keep mailboxes and state, making upgrades straightforward and rollbacks less risky. ...