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OPS335 Lab 4

118 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 you 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)
We will be using a simple text-based '''Mail User Agent (MUA)''' called '''mailx''' in this lab to '''both send and receive''' mail messages within your '''vm2''' machine and to '''only send''' mail messages from your '''vm2''' machine to your Seneca e-mail account.
'''NOTE:''' Due to the simplicity of this mail server setup Because you're using private IP addresses and the lack of other no external DNS servers are pointing to your network, and the setup of Seneca College's mail server, you '''<u>cannot</u>''' send Seneca e-mail messages from outside your environment to your '''vm2''' machine.
=== Installing the Mail User Agent (MUA)===
#Make certain you are in your '''vm2''' machine.
#Issue the following command to install Install the '''mailx''' application (MUA):<br>'''using yum install mailx'''<br><br>
:'''NOTE:''' You can refer to the link below to acquaint yourself on how to send e-mail messages using '''mailx''' application:<br> [http://www.simplehelp.net/2008/12/01/how-to-send-email-from-the-linux-command-line/ Mail Send Command Examples]
===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.
#Check your Seneca email account (Inbox / Junk Email Folder) to see if you got the email (note that it may take a <u>few minutes to arrive</u>, so you may also wish to try an alternate email account if you have one like gmail, etc). When you do receive that email, make a note of the return address.
#If you did not receive the mail, check the mail logs on your vm2 machine to determine any errors messages that would indicate a mail server setup problem.
#Once you have succeeded in sending the first email, send a second email to the same destination using the following command:<br>'''mail -r "someone@hacker.com (Canadian Revenue Agency)" -s "Lab4a - test2" <Your Seneca email address>
#Check your email to see if you got the email. If you did, make a note of the return address. How would you think that including the '''-r''' option could be used by penetration hackers to gain access to a computer system? What sort of steps do you think should be taken to help prevent this type of attack from happening?
'''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).
===Online Submission===Follow the instructions for lab 4a on blackboard.<!--===Andrew'''Depending s sections=== You may choose to:* Submit screenshots of your work on your professor Blackboard, in which case you will either be asked don't need to come to the lab.* Or come to submit the lab in class, or onlineshow me your work, and talk to me about it. Follow the appropriate set of instructions below''I want to hear what you've learned and answer any questions you have.
===Online Submission (Peter CallaghanYou's Classes only)===Follow ll get the instructions for lab 4a on blackboardsame grade regardless of how you choose to submit your work.
===In Class Submission (Murray Saul's Classes only)===
::<span style="color:green;font-size:1.5em;">&#x2713;</span>Arrange proof that you can send e-mail from your '''vm2''' machine to your '''Seneca College e-mail account''', and than you can '''send and receive e-mail messages between on your vm2 and vm3 machines'''.
::<span style="color:green;font-size:1.5em;">&#x2713;</span>Download the labcheck4a.bash checking bash shell script by issuing the command:<br><br>and run '''wget httphttps://matrixict.senecac.onsenecacollege.ca/~peterandrew.callaghansmith/files/OPS335ops335/labcheck4a.bash'''<br><br>set execute permission and run the shell script on your '''host''' machine. ::*For '''Peter's classes''', follow his Online Submission instructions in Moodle.::*For '''Murray's classes''', run command (piping to the '''more''' command) on both VM2 and VM3 and show output to instructor.
::<span style="color:green;font-size:1.5em;">&#x2713;</span>Completed Lab4a log-book notes.
-->
==EXPLORATION QUESTIONS==

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