SMTP — Configure an MTA to forward (relay) email through a smart host

This is a simple one, similar to defaulting to accept mail locally, by default postfix will only send mail to local recipients.

1. Install the necessary packages
1. yum install postfix 
2. Edit the /etc/postfix/main.cf file
1. Find the relayhost section and add a line relayhost = 192.168.10.1
3. Restart the service
1. service postfix restart

You should be able to test this by sending an email to a remote user.