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→Perform the following steps on your VM2 (pri-dns)
</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.
:** Run the following command pipe line and study the output carefully:
<pre>
[instructor@pri-dns ~]$ ps -ef | grep -v grep | grep postfixroot 122055 1 0 18:53 ? 00:00:00 /usr/libexec/postfix/master -wpostfix 122057 122055 0 18:53 ? 00:00:00 qmgr -l -t unix -upostfix 122105 122055 0 18:54 ? 00:00:00 tlsmgr -l -t unix -upostfix 122216 122055 0 20:33 ? 00:00:00 pickup -l -t unix -u
</pre>
:** Look up the man page for "qmgr", "tlsmgr", and "pickup", and find out the responsibility of those processes.
== Review the SMTP Protocol ==
# smtp commands/responses
