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Building your own emailServer (WTmail) - "Under constrution"

¿What is it?

It is a Linux mail server based on the protocols:

  • SMTP (Simple Mail Transfer Protocol)
  • POP3 (Post Office Protocol)
  • IMAP (Internet Message Access Protocol)

Development and testing tools

Operating system: Debian 9 64bit

No-ip

Thuderbird application

  • Packages:
  • Postfix
  • Spamassassin
  • Letsencrypt
  • Bsd-mailx
  • Procmail
  • dovecot-imapd, dovecot-pop3d, dovecot-lmtpd

Project results

Mail server with domain: wtmail.hopto.org

Automated script to install an encrypted mail server with a spam tray and also accept the three operating modes:

  • Online mode: direct access to emails
  • Offline mode: synchronize the tray by taking emails from the mail server
  • Disconnected mode: allow users to keep local copies of emails

Step 1

  1. Ask for the dynamic ip domain in No-ip (https://www.noip.com/)

  2. Configure the DNS record update in No-ip

  3. Download and demonize the noip2 script to start at system boot

     wget https://www.noip.com/client/linux/noip-duc-linux.tar.gz
 tar -xf noip-duc-linux.tar.gz
 cd noip-2.1.9-1/
 make
 make install
 cp debian.noip2.sh /etc/init.d/debian.noip2.sh 
 ln -s /etc/init.d/debian.noip2.sh /etc/rc0.d/K01debian.noip2.sh
 ln -s /etc/init.d/debian.noip2.sh /etc/rc1.d/K01debian.noip2.sh  
 ln -s /etc/init.d/debian.noip2.sh /etc/rc2.d/K01debian.noip2.sh  
 ln -s /etc/init.d/debian.noip2.sh /etc/rc3.d/K01debian.noip2.sh  
 ln -s /etc/init.d/debian.noip2.sh /etc/rc4.d/K01debian.noip2.sh
 ln -s /etc/init.d/debian.noip2.sh /etc/rc5.d/S01debian.noip2.sh
 ln -s /etc/init.d/debian.noip2.sh /etc/rc6.d/K01debian.noip2.sh  
 chmod 755 debian.noip2.sh
 systemctl start postfix
 systemctl enable postfix

Step 2

  1. Set private ip for the mail server
  2. Open NAT port to receive requests

Step 3

  1. Installl postfix:

     apt-get install postfix

Step 4

  1. Install procmail:

     apt-get install procmail

  2. Configure Postfix in /etc/postfix/main.cf

      echo "myhostname = $host_name" >> /etc/postfix/main.cf
  echo "mydomain = $host_name" >> /etc/postfix/main.cf
  echo 'myorigin = $mydomain' >> /etc/postfix/main.cf
  echo 'mydestination= $myhostname, localhost.$mydomain,$mydomain,mail.$mydomain,www.$mydomain' >> /etc/postfix/main.cf
  echo 'mail_spool_directory = /var/spool/mail' >> /etc/postfix/main.cf
  echo 'mynetworks = 127.0.0.0/8, 192.168.1.0/24' >> /etc/postfix/main.cf
  echo 'inet_protocols = ipv4' >> /etc/postfix/main.cf
  systemctl reload postfix
  postfix check

Step 5

  1. Implement the SPAM tray using "spamassassin"

      apt-get install spamassassin
  systemctl start spamassassin
  systemctl enable spamassassin

  2. Integrate in postfix and restart it

    echo ':0 hbfw' >> /etc/procmailrc
echo '| /usr/bin/spamc' >> /etc/procmailrc
echo 'mailbox_command = /usr/bin/procmail' >> /etc/postfix/main.cf
systemctl restart postfix

Step 6

  1. Secure the SMTP connection through TLS (Generating the certificate and the key using openssl)

     cd /etc/postfix
 openssl genrsa -des3 -out mail.key
 openssl req -new -key mail.key -out mail.csr
 cp mail.key mail.key.original
 openssl rsa -in mail.key.original -out mail_secure.key
 openssl x509 -req -days 365 -in mail_secure.csr -signkey mail_secure.key -out mail_secure.crt

  2. Add the TLS options to the Postfix configuration file /etc/postfix/main.cf

     cp mail_secure.crt /etc/postfix/
 cp mail_secure.key /etc/postfix/
 echo 'smtpd_use_tls = yes' >> /etc/postfix/main.cf
 echo 'smtpd_tls_cert_file = /etc/postfix/mail_secure.crt' >> /etc/postfix/main.cf
 echo 'smtpd_tls_key_file = /etc/postfix/mail_secure.key' >> /etc/postfix/main.cf
 echo 'smtp_tls_security_level = may' >> /etc/postfix/main.cf
 systemctl restart postfix

  3. Encrypt traffic using the free SSL certificate provider (Let's Encrypt)

     letsencrypt certonly --standalone -d "$host_name"
 postconf -e "mtpd_tls_cert_file = /etc/letsencrypt/live/$host_name/fullchain.pem"
 postconf -e "smtpd_tls_key_file = /etc/letsencrypt/live/$host_name/privkey.pem"
 systemctl restart postfix

Step 7

  1. Install Dovecot to integrate POP3 and IMAP

     apt-get install dovecot-imapd dovecot-pop3d dovecot-lmtpd

  2. Configure Dovecot in /etc/dovecot/conf.d/dovecot.conf

     systemctl start dovecot
 systemctl enable dovecot
 echo "protocols =  imap pop3 lmtp" >> /etc/dovecot/dovecot.conf
 echo "listen = *, ::" >> /etc/dovecot/dovecot.conf
 echo "userdb {" >> /etc/dovecot/dovecot.conf
 echo "driver = passwd" >> /etc/dovecot/dovecot.conf
 echo "}" >> /etc/dovecot/dovecot.conf
 echo "passdb {" >> /etc/dovecot/dovecot.conf
 echo "driver = passwd" >> /etc/dovecot/dovecot.conf
 echo "}" >> /etc/dovecot/dovecot.conf

  3. Modify generic Dovecot SSL certificates to Let's Encrypt certificates

     echo "mail_location = mbox:~/mail:INBOX=/var/mail/%u" >> /etc/dovecot/conf.d/10-main.conf
 echo "ssl_cert = </etc/letsencrypt/live/$host_name/fullchain.pem" >>  /etc/dovecot/conf.d/10-ssl.conf
 echo "ssl_key = </etc/letsencrypt/live/$host_name/privkey.pem" >> /etc/dovecot/conf.d/10-ssl.conf
 echo "ssl = yes" >> /etc/dovecot/conf.d/10-ssl.conf

Step 8

  1. Enable MX in No-ip

Step 9

  1. Text your email server