Configuring Postfix as a Gmail Relay on CentOS 6.4 -?.?

[branx86]

Installing Postfix is easy, just run this command as root:

yum install postfix mailx cyrus-sasl-plain

Configuring

Create a file named sasl_passwd in /etc/postfix. Replace smtp_user and smtp_passwd with their respective values.
           echo "smtp.gmail.com    user@gmail.com:Gmail_password" > /etc/postfix/sasl_passwd

You then hash that file so that the password is not stored in clear text. This command will create a file named sasl_passwd.db in the /etc/postfix/ directory.
      postmap hash:/etc/postfix/sasl_passwd

After that is done, add these to the bottom of /etc/postfix/main.cf. This is assuming that your root certificates installed from openssl are located in /etc/pki/tls/certs/ca-bundle.crt.

      smtp_sasl_auth_enable = yes
       smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
       smtp_sasl_security_options = noanonymous
       # Secure channel TLS with exact nexthop name match.
       smtp_tls_security_level = secure
       smtp_tls_mandatory_protocols = TLSv1
       smtp_tls_mandatory_ciphers = high
       smtp_tls_secure_cert_match = nexthop
       smtp_tls_CAfile = /etc/pki/tls/certs/ca-bundle.crt
       relayhost = smtp.gmail.com:587

After that is done, restart postfix:

    service postfix restart

Now test it to make sure it is working. Run this in the terminal:
    mail email@domain

Fill in the subject, put something in the body and then type a . on a blank line to end and hit enter.

If all went well, you should get an email at the email address you entered. If you do, you can delete the file that has the password.

rm /etc/postfix/sasl_passwd

If it did not work, check the log to see what happened.

tail /var/log/maillog