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SMTP auth relay with postfix

In case that your SMTP server has authentication (like Gmail), For this purpose we will use Postfix. I

Install the needed packages:

Ubuntu

apt-get install postfix mailutils libsasl2-2 ca-certificates libsasl2-modules

CentOS

yum update && yum install postfix mailx cyrus-sasl cyrus-sasl-plain
  • Set Postfix config file /etc/postfix/main.cf. Add this lines to the end of the file:
  1. Set Postfix config file /etc/postfix/main.cf. Add this lines to the end of the file:

    Ubuntu

    relayhost = [smtp.gmail.com]:587
    smtp_sasl_auth_enable = yes
    smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
    smtp_sasl_security_options = noanonymous
    smtp_tls_CAfile = /etc/ssl/certs/thawte_Primary_Root_CA.pem
    smtp_use_tls = yes
    

    CentOS

    relayhost = [smtp.gmail.com]:587
    smtp_sasl_auth_enable = yes
    smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
    smtp_sasl_security_options = noanonymous
    smtp_tls_CAfile = /etc/ssl/certs/ca-bundle.crt
    smtp_use_tls = yes
    
  2. Configure email address and password:

    echo [smtp.gmail.com]:587 USERNAME@gmail.com:PASSWORD > /etc/postfix/sasl_passwd
    postmap /etc/postfix/sasl_passwd
    chmod 400 /etc/postfix/sasl_passwd
    
  3. Secure DB password

    chown root:root /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db
    chmod 0600 /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db
    
  4. Reload Postfix

    systemctl reload postfix
  • Test you configuration with:

    echo "Test mail from postfix" | mail -s "Test Postfix" you@example.com
    echo "Test mail from postfix" | mail -s "Test Postfix" -r someone@whatever.com you@example.com (this is if your reply address has to come from a specific sender)
    

    You should receive an email on you@example.com

You should receive an email on you@example.com

Note: If you are using centos 7, which uses systemD. You will find that postfix doesn’t send maillogs to /var/log/maillog. Someone decided it would be a great idea to send it to the journaler instead.

In order to find your mail logs and or tail the logs for postfix.

  • Journalctl -u postfix (view all logs)
  • Journalctl -u postfix -f (to tail the mail logs)