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OPS335 Lab 4

240 bytes removed, 4 January
Sending a Mail Message from your vm2 Machine to your Seneca Email Account
We are going to spread the remaining email labs over a few weeks, so that by the end of this topic, you will have a sufficient understanding of what services are involved in sending, filtering, and reading email. You will also have the skills to configure a basic mail setup using the default services provided for your Centos7 Linux distribution.
Believe it or not, this is considered to be a simple diagram of how you can send sending an email to someone else:
[[Image:Email-servers.png]]
This lab will show you how to set up a Mail User Agent ('''MUA'''), using the '''mailx''' package on your '''vm2''' machine to send and receive e-mails on your local VM. In this case, the '''Postfix''' package which represents your '''MTA''' is most likely already installed and running on your local VM. In addition to sending and receiving emails on your Local VM, you will also be able to send a text-based e-mail from your '''vm2 machine''' to your '''Seneca mail account'''. You will also learn how to make multiple MTAs in the same network collaborate in sending emails. In addition, you will learn where the message store (MS) is located that stores mail messages until they are viewed and either deleted or transferred to other folders.
 
The '''diagram''' below shows the layout of the what this lab should be able to accomplish:
 
 
[[Image:email-setup-simple.png]]
Although, you will not be able to receive mail messages from outside sources (such as your Seneca email account), this lab acts as a starting point in order to run a basic email server. You are NOT required to go into tremendous depth (just the minimum requirements). For example, we will not go over every aspect of the Postfix MTA service, but you should know what it represents and what is its main purpose, as opposed to the following: [https://en.wikipedia.org/wiki/Postfix_%28software%29#Architecture complex diagram 1] , [https://www.credativ.de/blog/postfix-architecture-overview complex diagram 2].
===Online References:===
* [https://prezi.com/iuk-advzak_o/mail-servers-basic-concepts/ Email Servers: Basic Terms] (online slide notes)
* [http://www.simplehelp.net/2008/12/01/how-to-send-email-from-the-linux-command-line/ Mail Send Command] (examples how to send e-mail using mail command)
* [http://www.johnkerl.org/doc/mail-how-to.html#prompt_commands View and Manage Received e-mail Mesages] (Common commands to view and manage received email messages)
===Sending a Mail Message from your vm2 Machine to your Seneca Email Account===
{{Admon/important|Note|These instructions no longer work reliably. You can still send email to your own email server, and look at the server logs to see that it did really get sent. But it probably won't be accepted for one of a multitude of good reasons. If it doesn't work for you: don't worry about it for lab submission purposes.}}
We will now test to see if your MTA for your vm2 machine is correctly running by sending email messages from your vm2 machine to your Seneca e-mail account.
'''Perform the following Steps:'''
#Send an email message locally (i.e. only within) your vm2 machine ) by issuing the command:<br>'''mail -s "Lab4a - Local - Test1" <yourSenecaID>'''
#After you type in the body of the mail message, move to an empty line, type period "." and press the ENTER key to send the message.
#Issue Login with your '''regular user''' and issue the following command to read the mail message you send to yourself:<br>'''mail'''<br><br>'''NOTE:''' You can refer to the link below to view a reference chart on how to read and delete received e-mail messages at the mail command prompt:<br>[http://www.johnkerl.org/doc/mail-how-to.html#prompt_commands Commands to View and Manage Received e-mail Mesages]<br><br>
#Issue the following command: '''cat /var/spool/mail/<yourSenecaID>'''<br>What do you see? What does this show you in terms of where mail is stored on your e-mail server?
#If you received an e-mail message, the message and subject line should appear as a listing in your mail command.<br><br>'''NOTE:''' If you did not receive a mail message, check your mail server settings, check to see if you your mail server is running and also check '''/var/log/maillog''' and '''/var/log/messages'''(this step requires '''root''' privilege).<br><br>
#Once you have received the message, type the mail message number that is displayed in your e-mail message list in the prompt and press ENTER. You should be able to confirm the message body that you sent.
#Exit the mail program by typing the letter '''q''' and press ENTER.
# 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>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>mydomain = yoursenecaid.ops</source>
# Also you must set the '''hostname''' for this server so that will correctly specify the hostname in the '''From:''' head header in a sent mail message.<br>Make certain the following parameter only appears once (shown below):<source>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.
<br>
# Once that is complete, send an email from '''root on vm2''' to '''root on vm3''', and then reply '''from vm3 to vm2'''.
# If both messages arrive, both MTAs are working. If not, use the troubleshooting tools and techniques you have already learned to diagnose and fix the problem.<br><br>
{{Admon/important |Backup your VMs!|You MUST perform a '''full backup''' of ALL of your VMs whenever you complete your '''OPS335 labs''' or when working on your '''OPS335 assignments'''. You should be using the dump or rsync command, and you should use the Bash shell script that you were adviced to create in order to backup all of your VMs.}}
<br>
'''Record steps, commands, and your observations in INVESTIGATION 3 in your OPS335 lab log-book'''
 
==COMPLETING THE LAB==
Upon completion of this lab you should have postfix mail servers running on two machines, and starting automatically when they do. These servers must have sent email both ways between each other (from vm2 to vm3, and from vm3 to vm2), and to your seneca email (or other external mail server).
'''Depending on your professor you will either be asked to submit the lab in class, or online. Follow the appropriate set of instructions below''' ===Online Submission (Ahad Mammadov's Classes only)===
Follow the instructions for lab 4a on blackboard.
<!--
===Andrew's sections===
::<span style="color:green;font-size:1.5em;">&#x2713;</span>Download and run '''https://ict.senecacollege.ca/~andrew.smith/ops335/labcheck4a.bash''' on your '''host''' machine.
::<span style="color:green;font-size:1.5em;">&#x2713;</span>Completed Lab4a log-book notes.
-->
==EXPLORATION QUESTIONS==

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