sendmail

#!/bin/sh
# shellcheck disable=SC2086

MAILFROM=${MAILFROM:-sendmail}
SMTP_HOSTNAME=${SMTP_HOSTNAME:-smtp-relay.gmail.com}
SMTP_USERNAME=${SMTP_USERNAME:-}
SMTP_PASSWORD=${SMTP_PASSWORD:-}
SMTP_TLS=${SMTP_TLS:-1}
SMTP_STARTTLS=${SMTP_STARTTLS:-0}
SMTP_PORT=${SMTP_PORT:-25}
SMTP_TLS_PORT=${SMTP_TLS_PORT:-465}

OPTIONS="-f $MAILFROM"

if [ -n "$SMTP_USERNAME" ]
then
	OPTIONS="$OPTIONS -au${SMTP_USERNAME}"
fi

if [ -n "$SMTP_PASSWORD" ]
then
	OPTIONS="$OPTIONS -ap${SMTP_PASSWORD}"
fi

if [ -z "$SMTP_TLS" ] || [ "$SMTP_TLS" = 0 ]
then
	exec /usr/sbin/sendmail $OPTIONS -S $SMTP_HOSTNAME:$SMTP_PORT "$@"
elif [ -n "$SMTP_STARTTLS" ] && [ ! "$SMTP_STARTTLS" = 0 ]
then
	exec /usr/sbin/sendmail $OPTIONS -H "openssl s_client -quiet -tls1 -starttls smtp -connect $SMTP_HOSTNAME:$SMTP_TLS_PORT" "$@"
else
	exec /usr/sbin/sendmail $OPTIONS -H "openssl s_client -quiet -tls1                -connect $SMTP_HOSTNAME:$SMTP_TLS_PORT" "$@"
fi