Understanding master.cf
Configure Postfix services, listeners, chroot behavior, process limits, and service overrides.
Production note: Back up configuration, run
postfix check, and stage changes before reloading.Service fields
Each non-comment line defines service name, type, privacy, unprivileged mode, chroot, wakeup, process limit, command, and arguments.
Submission service
submission inet n - n - - smtpd
-o syslog_name=postfix/submission
-o smtpd_tls_security_level=encrypt
-o smtpd_sasl_auth_enable=yes
-o smtpd_recipient_restrictions=permit_sasl_authenticated,rejectValidation
Use postfix check and postfix reload. Inspect service startup failures in the journal.
Common mistakes
Incorrect continuation indentation, conflicting overrides, enabling submission without authentication, and assuming chroot paths contain required files.