postfix-relay.sh

#!/bin/sh

SMTP_HOST=smtp.domain.ltd
SMTP_USER=user
SMTP_PASSWORD=ToPs3cR3t

# Edit main.cf
postconf -e 'mydestination = $myhostname, localhost.$mydomain, localhost'
postconf -e 'smtp_generic_maps = hash:/etc/postfix/smtp_maps'
postconf -e "relayhost = $SMTP_HOST"
postconf -e 'smtp_sasl_password_maps = hash:/etc/postfix/_smtp_sasl_password_maps'
postconf -e 'smtp_sasl_auth_enable = yes'
postconf -e 'smtp_sasl_security_options = noanonymous'
postconf -e 'smtp_tls_security_level = encrypt'
postconf -e 'smtp_use_tls = yes'
postconf -e 'canonical_maps = regexp:/etc/postfix/_canonical_maps'
postconf -e 'canonical_classes = envelope_sender'
postconf -e 'inet_protocols = ipv4'

# Create smtp config
echo "root $SMTP_USER" > /etc/postfix/smtp_maps
## Use the empty regexp to map *any* address to the desired envelope sender.
echo "// $SMTP_USER" > /etc/postfix/_canonical_maps
echo "$SMTP_HOST ${SMTP_USER}:$SMTP_PASSWORD" > /etc/postfix/_smtp_sasl_password_maps
chown root:root /etc/postfix/smtp_sasl_password_maps /etc/postfix/smtp_maps /etc/postfix/_canonical_maps
chmod 400 /etc/postfix/smtp_sasl_password_maps /etc/postfix/smtp_maps /etc/postfix/_canonical_maps

# Create Berkeley db files
postmap /etc/postfix/_smtp_sasl_password_maps
postmap /etc/postfix/smtp_maps
postmap /etc/postfix/_canonical_maps