entrypoint.sh

#!/bin/sh
set -e

# Avoid  warning: smtputf8_enable is true, but EAI support is not compiled in
echo "smtputf8_enable = no" >> /etc/postfix/main.cf

cat >> /etc/postfix/main.cf << EOF
# limit smtp to loopback interface & compute engine doesn't support ipv6
inet_protocols = ipv4
EOF

# Do we want to modify the config first with the script?
# shellcheck disable=SC1091
[ -f /etc/service/postfix/run.config ] && source /etc/service/postfix/run.config

if [[ -n "$MAILNAME" ]]; then
	echo "$MAILNAME" > /etc/mailname
	postconf -e myorigin="/etc/mailname"

	cat >> /etc/postfix/main.cf <<- EOF
	# Force ehlo behavior
	smtp_always_send_ehlo = yes
	smtp_helo_name = $MAILNAME
	EOF
fi

if [[ -n "$MY_NETWORKS" ]]; then
	postconf -e mynetworks="$MY_NETWORKS"
fi

if [[ -n "$MY_DESTINATION" ]]; then
	postconf -e mydestination="$MY_DESTINATION" 
fi

if [[ -n "$ROOT_ALIAS" ]]; then
	if [[ -f /etc/aliases ]]; then
		sed -i '/^root:/d' /etc/aliases
	fi
	echo "root: $ROOT_ALIAS" >> /etc/aliases
	newaliases
fi

if [[ -n "$RELAY" ]]; then
	# setup the relay
	cat >> /etc/postfix/main.cf <<- EOF
	relayhost = $RELAY

	# These lines can be used, if the result is not as expected
	debug_peer_list = smtp-relay.gmail.com
	debug_peer_level = 2
	EOF
fi

if [[ -n "$TLS" ]]; then
	# setup tls
	cat >> /etc/postfix/main.cf <<- EOF
	smtp_use_tls = yes
	smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt
	EOF
fi

if [[ -n "$SASL_AUTH" ]]; then
	cat >> /etc/postfix/main.cf <<- EOF
	smtp_sasl_auth_enable = yes
	smtp_sasl_password_maps = lmdb:/etc/postfix/sasl_passwd
	smtp_sasl_security_options = noanonymous
	EOF

	# generate the SASL password map
	echo "$RELAY $SASL_AUTH" > /etc/postfix/sasl_passwd

	# generate a .db file
	postmap /etc/postfix/sasl_passwd

	# cleanup
	rm /etc/postfix/sasl_passwd

fi

if [[ -f "/usr/libexec/postfix/master" ]]; then
	cmd="/usr/libexec/postfix/master"
fi

if [[ -f "/usr/lib/postfix/master" ]]; then
	cmd="/usr/lib/postfix/master"
fi

if [[ -z "$cmd" ]]; then
	echo "Could not find postfix master in /usr/lib or /usr/libexec"
	exit 1
fi

postconf -e maillog_file="/dev/stdout"

exec postfix start-fg