#!/bin/bash
# author: Timo Stankowitz <timo.stankowitz@gmail.com>
# create date: 2016-08-15
# last change: 2016-08-15

# Dieses Script konfiguriert Postfix so, dass mailgun (oder andere) als e-mail relay konfiguriert wird
# somit werden e-mails über mailgun, und nicht direkt von Postfix gesendet.
# Dies hat den Vorteil, dass die e-mails nicht im Spam Ordern, oder überhaupt nicht beim client landen.

postfixMainConfig="/etc/postfix/main.cf"
postfixSaslPasswdFile="/etc/postfix/sasl_passwd"

fqdn=$(hostname).example.de
relayhost="smtp.mailgun.org"
relayhostPort=587
smtpUserName="username@example.com"
smtpUserPassword=""

# first check if the user is root
if [ "$(id -u)" != 0 ]; then
   echo "Please execute this script as root"
   exit 1
fi

# check if postfix is installed on the system
if [ ! -f $postfixMainConfig ]; then
   printf "Postfix is not installed. Do you wish to install postfix now? (Y/n): "
   read

   case $REPLY in
      yes|Yes|y|Y|j|J|'')
	 echo "Installing Postfix now"
	 echo "Please select 'Internet Site' for the postfix configuration"
	 echo "and after that press enter for the hostname"
	 sleep 5

	 # check if apt-get is installed on the system
	 which apt-get > /dev/null 2>&1
	 checkAptGetExists=$?
	 if [ "$checkAptGetExists" != 0 ]; then
	    echo "ERROR: apt-get is not installed on your system."
	    printf "Please install apt-get on your system. \nEXIT"
	    exit 1
	 fi

	 apt-get update
	 apt-get install postfix -y
	 ;;

      n|N|no)
	 echo "Please install postfix manually."
	 exit 1
	 ;;
   esac
fi

echo
printf "Please Enter your FQDN [$fqdn]: "
read

if [ "$REPLY" != '' ]; then
   fqdn=$REPLY
fi

echo "set FQDN to $fqdn"
echo
printf "Please set your relayhost [$relayhost]: "
read

if [ "$REPLY" != '' ]; then
   relayhost=$REPLY
   echo "set relayhost to $relayhost"
   echo
   printf "Please set to port of the relayhost [$relayhost] : "
   read

   if [ "$REPLY" != '' ]; then
      relayhostPort=$REPLY
      echo "set port to $relayhostPort"
   fi
fi

echo "set relayhost to $relayhost"
echo
printf "Please set the smtp username [$smtpUserName]: "
read smtpUserName
echo "smtp username set to $smtpUserName"
echo
printf "Please set the smtp user password (will be displayed in plaintext): "
read smtpUserPassword
echo "smtp user password set to $smtpUserPassword"

# checking configuration
echo
echo "here is your configuration: "
echo
echo "FQDN: $fqdn"
echo "smtp relay host: $relayhost"
echo "smpt relay host port: $relayhostPort"
echo "smtp username: $smtpUserName"
echo "smpt user password: $smtpUserPassword"
echo
printf "is everything fine? (Y/n): "
read

case $REPLY in
   yes|Yes|y|Y|j|J|'')
      ;;

   n|N|no)
      "oh shit... sorry... try again... EXIT"
      exit 1
      ;;
esac

# create a backup of the existing postfix conf file
echo "creating a backup of the orig config file"
cp $postfixMainConfig $postfixMainConfig.orig

# working on the postfix config file
# deleting those entries
sed -i '/appending .domain is the/d' $postfixMainConfig
sed -i '/append_dot_mydomain/d' $postfixMainConfig
sed -i '/relayhost/d' $postfixMainConfig
sed -i '/myhostname/d' $postfixMainConfig
sed -i '/mydestination/d' $postfixMainConfig

# append to the config file
echo								     >> $postfixMainConfig
echo "# custom stuff"						     >> $postfixMainConfig
echo "append_dot_mydomain = yes"				     >> $postfixMainConfig
echo								     >> $postfixMainConfig
echo "myhostname = $hostname"					     >> $postfixMainConfig
echo "mydestination = $hostname, localhost.localdomain, localhost"   >> $postfixMainConfig
echo								     >> $postfixMainConfig
echo "relayhost = [$relayhost]:$relayhostPort"			     >> $postfixMainConfig
echo "smtp_sasl_auth_enable = yes"			       	     >> $postfixMainConfig
echo "smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd" 	     >> $postfixMainConfig
echo "smtp_sasl_security_options = noanonymous"		       	     >> $postfixMainConfig
echo "smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt"    	     >> $postfixMainConfig
echo "smtp_use_tls = yes"				       	     >> $postfixMainConfig

echo "[$relayhost]:$relayhostPort $smtpUserName:$smtpUserPassword"   > $postfixSaslPasswdFile
postmap $postfixSaslPasswdFile

# change permission
chmod 600 /etc/postfix/sasl_passwd*

echo
echo "Configuration is now done. Restarting postfix now..."
sleep 2
/etc/init.d/postfix restart

# check if mailutils are installed
which mail > /dev/null 2>&1
checkMailInstalled=$?
if [ "$checkMailInstalled" != 0 ]; then
   echo
   printf "mail tools are not installed on your system. Do you wan't to install the tools now? (Y/n): "
   read

   case $REPLY in
      yes|Yes|y|Y|j|J|'')
	 apt-get install mailutils -y
	 ;;

      n|N|no)
	 echo "okay - please install the tools manualy and send a test mail."
	 ;;
   esac
fi

echo
echo "DONE. now you can test the configuration by sending a testmail."
echo "echo "this is just a test" | mail -s "[test] just a test" foobar@example.com"
echo
echo "If you receve any error check /var/log/syslog. "

exit 0