= Investigation 1: SMTP =
== Perform the following steps on your VM2 (pri-dns):==
:* login to your VM2 as the student user.
# :* Find out the version of the postfix rpm installed on the system with one of the following commands and keep a record of it.<pre>rpm -q postfix version# yum info postifx</pre>:* SMTP servers use one of the well-known ports, you can find out the port number used by the smtp portprotocol with the following command:<pre># grep -w smtp status/etc/services</pre>: * Make sure that the postfix.service is running on VM2, if not, start the postfix.service and confirm that it is running properly.:*:* Beside the systemctl command, there are two more places (or commands) you can use to confirm whether there is a SMTP server running on your system: the "ss -at" and "ps -ef" command::** Run the following command pipe line and look for the SMTP port number under the "Local Address" column and record the line(s) for future reference. Note that if the Local Address shown is 127.0.0.1 only, your SMTP server will not be reachable by other machines.<pre>ss -at | grep smtp ss -atn | grep [smtp port number]</pre>:** Run the following command pipe line and study the output carefully:<pre>ps -ef| grep -v grep | grep postfix</pre>== Review the SMTP Protocol ==
# smtp commands/responses
# postfix main configuration file: /etc/postfix/main.cf
