Installing Postfix

Run the following commands:

sudo apt-get update
sudo apt-get install postfix

Configuring Postfix

  1. Run the following command: 
    sudo dpkg-reconfigure postfix

    Configuration questions:

    1. Select OK to proceed.
    2. Choose Satellite system.
    3. System Mail Name: <EMAIL_DOMAIN>
    4. SMTP relay host: <RELAY_HOST>

      Where RELAY_HOST must include the port number (e.g. 192.168.1.1:465).

    5. Root and postmaster mail recipient: root
    6. Other destinations to accept mail for: <EMAIL_DOMAIN>, localhost.localdomain, localhost
    7. Force synchronous updates on mail queue? No
    8. Local networks: 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
    9. Mailbox size limit (bytes): 0
    10. Local address extension character: +
    11. Internet protocols to use: all

      Feel free to answer the preceding questions based on your setup. Just replace the EMAIL_DOMAIN (i.e. example.com) with a valid value.

  2. Create the file /etc/postfix/sasl_passwd with the following content: 
    <RELAY_HOST> username:password
  3. Create a postfix database based on /etc/postfix/sasl_passwd using the following command: 
    sudo postmap /etc/postfix/sasl_passwd
  4. Edit the file /etc/postfix/main.cf to have the following entries added or updated: 
    smtp_tls_security_level = encrypt
smtp_sasl_auth_enable = yes
smtp_tls_wrappermode = yes
smtp_sasl_security_options =
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
  5. Restart the postfix service with the following command: 
    sudo systemctl restart postfix