anchor.diff:      net-tools \
       debconf-utils
   
  -# passing arguments to build postfix image 
  +# passing arguments to build postfix image
   ARG relay_ip
   ARG host_name
   ARG domain
  
positive.code: run echo "postfix postfix/mailname string $host_name" | debconf-set-selections
  run echo "postfix postfix/main_mailer_type string 'Internet Site'" | debconf-set-selections
  run apt-get update && apt-get install -y postfix
  run postconf -e relayhost=$relay_ip 
  run postconf -e myhostname=$host_name
  run postconf -e mydomain=$domain
  run postconf -e smtp_generic_maps=hash:/etc/postfix/generic
  run postconf -e mynetworks="127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 172.18.0.0/16" 
   
  # This will replace local mail addresses by valid Internet addresses when mail leaves the machine via SMTP. so please change it according to container.
  run echo "root@aa7fde2ee7f1 iotmail@example.com" > /etc/postfix/generic
  run postmap /etc/postfix/generic
  
  # mail command would be used for sending mails
  run apt-get install -y mailutils 
  
  # Start the postfix daemon during container startup
  RUN mkdir -p /etc/my_init.d
  COPY postfix.sh /etc/my_init.d/postfix.sh
  RUN chmod +x /etc/my_init.d/postfix.sh
  
  
  
negative.code: #
  # Dockerfile for building POSTFIX
  #
  # Build the Postfix  using phusion base image
  FROM phusion/baseimage
  
  # some basic package installation for troubleshooting
  RUN apt-get update && apt-get install -y \
  