Postfix main.cf Complete Guide

Use postconf

Prefer postconf for inspecting effective values and scripted changes. Keep comments explaining site-specific decisions in version-controlled configuration.

Identity parameters

myhostname = mail.example.com
mydomain = example.com
myorigin = $mydomain
inet_interfaces = all
inet_protocols = all

Relay policy

mynetworks = 127.0.0.0/8, [::1]/128
smtpd_relay_restrictions =
    permit_mynetworks,
    permit_sasl_authenticated,
    reject_unauth_destination

Routing

Use transport maps and sender-dependent relay maps only when the routing goal is clear. Test map lookups directly before reloading.

TLS

Choose TLS policy based on whether the service is public SMTP, authenticated submission or a controlled relay path. Do not blindly require encryption on port 25, where opportunistic TLS is the interoperable norm.

Validation

postfix check
postconf -n
postmap -q example.com hash:/etc/postfix/transport
systemctl reload postfix