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changing domain to .ops
We will be using the '''Postfix''' application as the '''MTA''', and we will be setting it up on your '''vm2''' and '''vm3''' machines. They will act as the "sending" email servers for your internal network. You will be able to send email out of your network, and receive email from within your network, but you will '''<u>not</u>''' receive email from outside of your network due to the following reasons:
* Individuals outside of your domain will never find the MX records because there are no '''.org''' other DNS servers pointing to your DNS server (i.e. you haven't paid for it).
* Even if the individuals could read your MX records, your local network is using IP addresses on a '''private subnet''', which is not routeable on the Internet, so it cannot be reached from outside of your system.
# If the '''nc''' command is not installed on your vm2 machine, install it (install '''nc''' command for your '''centos3''' vm as well).
# Connect from your '''vm2''' to itself using the '''nc''' command by issuing the following command:<br><source lang="bash">nc localhost 25</source>
# You should see a response: <br><source lang="bash">220 vm2.yourdomain.org ops ESMTP Postfix</source>
# You could theoretically use SMTP commands to send an email here, but this would be a very unusual use of your mail server. You have an '''MUA''' for a reason.
#Enter the command '''QUIT''' to close the connection to the server, then '''<ctrl>-c''' to terminate the nc command.
# In your '''vm2''' machine, launch in editing session for the postfix configuration file called: '''/etc/postfix/main.cf'''
# Our first editing change to the Postfix configuration will be to make the service "listen" for incoming connections on the external interface (i.e '''eth0''' from the VMs point of view).<br>Change the value of the following parameter to what is displayed below:<br><source lang="bash">inet_interfaces = all</source>
# We should also set the string that will end up in the '''From:''' header in messages sent by this server.<br>Change the '''mydomain''' option to YOUR domain name (shown below):<source lang="bash">mydomain = yoursenecaid.orgops</source>
# Also you must set the '''hostname''' for this server so that will correctly specify the hostname in the '''From:''' head in a sent mail message.<br>Make certain the following parameter only appears once (shown below):<source lang="bash">myorigin = $myhostname</source>
#Ensure that your '''hostname''' and '''DOMAIN''' name is properly set on your machine, otherwise you will need to set the '''myhostname''' parameter.