#!/bin/bash
MESSAGE=$(cat -)
LOGFILE="/tmp/mail.log"

write_logfile() {
    echo "$1" >> $LOGFILE
}

write_deadletter() {
    echo "$MESSAGE" >> /tmp/deadletter
    echo "----------------------------------------------------" >> /tmp/deadletter
}

# read ssmtp.conf
HOST=$(cat /etc/ssmtp.conf)
if [[ ! "$HOST" =~ ^(hostname)\ ([0-9]+\.[0-9]+\.[0-9]+\.[0-9]+) ]]; then
  write_deadletter
  write_logfile "$(date +'%d-%m-%Y %T') SMTP server problem Connection refused. mail was saved in file /tmp/deadletter"
  exit 1
else
  HOST=${BASH_REMATCH[2]}
fi

# check if from in header
[ "$(echo "$MESSAGE" | sed -n '/^$/q;/^from:/Ip')" ] || ARGS="on"

# check if replyto
if [[ "$(echo "$MESSAGE" | sed -n '/^$/q;/^reply-to:/Ip')" ]]; then
  REPLYTO=$(echo "$MESSAGE" | grep -E "[rR]eply-[Tt]o:" | cut -d: -f2- | sed 's/ //1')
  LOG_REPLYTO="reply-to=$REPLYTO"
fi

OUT=$(echo "$MESSAGE" | msmtp \
  --host=${HOST} \
  --maildomain=localhost \
  --auto-from=${ARGS:-off} \
  --read-envelope-from \
  --read-recipients \
  --set-from-header=auto \
  --set-date-header=auto \
  --undisclosed-recipients=off \
  --logfile=- \
  --logfile-time-format="%d-%m-%Y %T" \
  $@ 2>/dev/null)

EXITCODE=$?
case $EXITCODE in
  65)
    [[ $OUT =~ ^([0-9\-]+)\ ([0-9:]+)\ .+\ (from=.+)\ (recipients=.+)\ smtpstatus=.+\ (smtpmsg=.+)\ (errormsg=.+)\ exitcode ]] && write_logfile "${BASH_REMATCH[@]:1} $LOG_REPLYTO"
    ;;
  69)
    [[ $OUT =~ ^([0-9\-]+)\ ([0-9:]+)\ .+\ (from=.+)\ (recipients=.+)\ smtpstatus=.+\ (smtpmsg=.+)\ (errormsg=.+)\ exitcode ]] && write_logfile "${BASH_REMATCH[@]:1} $LOG_REPLYTO"
    write_deadletter "$MESSAGE"
    ;;
  *)
    [[ $OUT =~ ^([0-9\-]+)\ ([0-9:]+)\ .+\ (from=.+)\ (recipients=.+)\ mailsize=.+\ (smtpmsg=.+)\ exitcode ]] && write_logfile "${BASH_REMATCH[@]:1} $LOG_REPLYTO"
    ;;
esac