# /etc/postfix/main.cf

# Use maildrop as MDA.
mailbox_command = /usr/bin/maildrop

# Restrictive relaying policy.
smtpd_relay_restrictions = permit_mynetworks defer_unauth_destination

# What domains to receive mail for: names of local server.
mydestination = HOSTNAME, localhost

# What clients to relay mail from: only local server.
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128

# Paranoid maximum error notification.
notify_classes=2bounce, bounce, data, delay, policy, protocol, resource, software