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==MAIL SERVER RESOURCESOVERVIEW & PREPARATION==

* [https://prezi.com/iuk-advzak_o/mail-servers-postfix/ OPS335 Mail Server Notes ] Course Note providing Concepts 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 Overview of mail server setup* [http://www.fredshack.com/docs/postfix.html Postfix for Dummies] Good Basic Guide to setup Postfix MTA* [http://wwwreading email.simplehelp.net/2008/12/01/how-to-send-email-from-You will also have the-linux-command-line/ Mail Send Command] (examples how skills to send e-configure a basic mail setup using mail command)* [http://wwwthe default services provided for your Centos7 Linux distribution.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)

==OVERVIEW & PREPARATION==This lab will show you how to set up a '''Postfix''' email server ('''MTA''') on your '''VM2''' machine to send an e[[Image:Email-mail message to an '''external e-mail server (i.e. myseneca.ca)'''. You will also be setting up on your '''VM2'''machine the '''mailx''' package ('''MUA''') to allow users of that VM to send a text-based e-mail to your Seneca mail account (only send, but not receive), and to send and receive e-mails locally on your VM2 machineservers.png]]

In order 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-mail messages mails on your local VM. In this case, the '''Postfix'''between package which represents your different VMs'''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 more complex settext-based e-up is requiredmail 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, and you will be addressed in learn where the second part of lab4message store (MS) is located that stores mail messages until they are viewed and either deleted or transferred to other folders.

The '''diagram''' below shows 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 layout 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 this lab should be able is its main purpose, as opposed to accomplishthe following:[https://en.wikipedia.org/wiki/Postfix_%28software%29#Architecture complex diagram 1] , [https://www.credativ.de/blog/postfix-architecture-overview complex diagram 2].

* [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)* [Imagehttp:email//www.johnkerl.org/doc/mail-setuphow-simpleto.html#prompt_commands View and Manage Received e-mail Mesages] (Common commands to view and manage received email messages)* [https://support.google.pngcom/mail/answer/29436?hl=en Reading Full Email Headers](Explanation of message header information)* [http://wiki.dovecot.org/MailServerOverview Here's an overview](common mail server terms)

==INVESTIGATION 1: INSTALL & SETUP THE MAIL TRANSFER AGENT 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 '''MTAvm2''')==machine to your Seneca e-mail account.

{{Admon/important|Prerequistites|<ol><li>Ensure <u>all</u> machines have been updated and that the '''clocks NOTE:''' Because you're using private IP addresses and no external DNS servers are set pointing to the correct date and timeyour network, you '''.<bru>cannot</liu><li>Due ''' send e-mail messages from outside your environment to the changes made in this lab3, your '''you will now need your vm1 running (as the DNS server)vm2''' in order for any of your virtual machines to be able to use the internetmachine.</li></ol>}}

=== Confirm Network Connections Installing the Mail User Agent (MUA)===

Before proceeding with this lab, we need to confirm our machines have connectivity to '''Perform the Internet before we can install and start sending e-mail messages.following Steps:'''

#Make certain you are in your '''Perform vm2''' machine.#Install the following steps'''mailx''' application (MUA) using yum:'''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]

#Make certain that you can connect to the Internet on ===Sending a Mail Message from your '''Host vm2 Machine''' via web-browser.<br> Since your host should be using '''VM1''' as its '''DNS server''', you will need to make certain that the '''VM1''' machine is running as well.#Start a web-browser on your '''Host Machine''', and access your Seneca e-mail account (https://myseneca.ca).#Confirm that you can access the web from your '''VM2''' machine. You can install the '''wget''' or '''lynx''' applications in order to test this for your text-based server.Email Account===

===Install {{Admon/important|Note|These instructions no longer work reliably. You can still send email to your own email server, and Configure Postfix Package (MTA) on look at the server logs to see that it did really get sent. But it probably won't be accepted for one of a VM===multitude of good reasons. If it doesn't work for you: don't worry about it for lab submission purposes.}}

We will now be installing the '''postfix application''' which will act as the Mail Transfer Agent ('''test to see if your MTA''') that will send e-mail for your vm2 machine is correctly running by sending email messages from your vm2 machine to other your Seneca e-mail servers.<br>In our case, between our servers '''vm2''' and an outside server which is your '''Seneca College''' email account (https://myseneca.ca).

#Switch to Make certain you are still in your '''VM2vm2''' machine.#Check the status of the Test email from your machine by sending an email to your '''sendmailSeneca email account''' service by using the '''systemctl''' command. If the sendmail service is running, use the ''systemctl'' command to stop and disable that service. #Issue the following command to install the '''postfix''' application (MTA):<br>'''yum install postfix'''<br><br>#What is the purpose of installing the postfix application in terms of using email -mail? Record your answer in your lab logbook.#We need to <u>configure</u> our MTA (postfix application) to recognize our recentlys "Lab4a -created domain name that was created in lab3.test1" <brYour Seneca email address>Edit the Postfix configuration file called '''/etc/postfix/main.cf''' replacing the existing contents with only the contents displayed below:<br><br>'''mydomain = senecaID.orgNOTE:'''<br>after you type in the body of the mail message, move to an empty line, and then press the key combination '''myorigin = $mydomain&lt;ctrl&gt;&lt;d&gt;'''<br>'''mynetworks = 127.0.0to send the message.0/8, 192.168.X.0/24'''<br>'''relay_domains ='''<br>'''inet_interfaces=all'''#Check your Seneca email account (Inbox / Junk Email Folder) to see if you got the email (note that it may take a <bru>few minutes to arrive<br/u>Your MTA has the ability to resolve "fake" public address , so you may also wish to try an actual user alternate email account name. For example, if you have a user account called "msaul"one like gmail, etc). When you can have the MTA resolve the fake name "murray.saul" to the account name "msaul". In order to do thisreceive that email, you will need to create an '''alias''' which is contained in make a note of the MTA's alias filereturn address.<br><br>#Edit If you did not receive the mail, check the '''/etc/postfix/aliases''' file and add mail logs on your first name as an alias vm2 machine to be resolved to your VM2's account name:<br><br>'''your-first-name''' &nbsp; &nbsp; &nbsp; '''your-vm2-regular-username'''<br><br>determine any errors messages that would indicate a mail server setup problem.#In order Once you have succeeded in sending the first email, send a second email to update the MTA's database for the newly-create alias, issue same destination using the following command:<br>'''postalias hash:/etc/aliases'''mail -r "someone@hacker.com (Canadian Revenue Agency)" -s "Lab4a - test2" <br><brYour Seneca email address>#Finally, Check your email to start and enable your MTAsee if you got the email. If you did, issue make a note of the following commands:<br>'''systemctl start postfixreturn address.service'''<br>'''systemctl enable postfix.service'''<br><br>#Check How would you think that including the '''/var/log/messages-r''' file option could be used by penetration hackers to see that your MTA server started without error. If there are any errors, correct them before continuing.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?

We will now test both your MUA (mailx) and MTA (postfix) by sending and receiving e-mail messages on the local vm2 machine only. '''Record steps, commands, and your observations in INVESTIGATION 1 in your OPS335 lab log-bookPerform the following Steps:'''

==INVESTIGATION 2: INSTALL &amp; SETUP THE MAIL USER AGENT ('''MUARecord steps, commands, and your observations in INVESTIGATION 1 in your OPS335 lab log-book''')==

We will be using a simple text-based Mail User Agent ==INVESTIGATION 2: SETUP MTA TO SEND MAIL MESSAGES ('''MUA'''NO ENCRYPTION) called '''mailx''' in this lab to '''send and receive mail messages within your VM1 machine''' and to '''send mail messages to your Seneca e-mail account'''.==

We will be using the '''NOTE:Postfix''' Due to application as the simplicity of this mail server setup'''MTA''', and we will be setting it up on your '''vm2''' and '''vm3''' machines. They will act as the setup "sending" email servers for your internal network. You will be able to send email out of Seneca College's mail serveryour network, and receive email from within your network, but you will '''<u>cannotnot</u>''' send Seneca 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 other DNS servers pointing to your DNS server (i.e-mail messages to . you haven't paid for it).* Even if the individuals could read your MX records, your local network is using IP addresses on a '''VM2private subnet''' machine, which is not routeable on the Internet, so it cannot be reached from outside of your system.

=== Installing Verify the Mail User Agent (MUA)Postfix Service Status ===

'''Perform the following Stepssteps:'''

#Make certain you are in your The '''postfix'vm2''application should be installed by default. If it isn' machinet, install it.#Postfix is capable of sending email with the default configuration, so start and enable this service, and verify that the postfix service is running.#Issue Look for the running postfix service in the list of listening ports by issuing the following command to install the '''mailx''' application (MUA):<br>'''yum install mailx'''<brsource>ss -atnp<br/source>:'''NOTE:''' You can refer to #Which service is postfix running? Locate the port used by SMTP, and look for connections with the link below to acquaint yourself on how to send state LISTEN (i.e-mail messages using '''mailx''' application:<br> [http://www.simplehelpcurrently listening).#Write your observations in your lab logbook.net/2008/12/01/how-to-send-email-from-the-linux-command-line/ Mail Send Command Examples]

===Testing mail with the internetconnection to the Postfix Service ===

We will now be demonstrating the use of the '''nc''' application to test to see if your MTA for your VM2 machine that the postfix service is correctly running by sending email messages from your VM2 machine to your Seneca e-mail accountand listening.

#Make certain you are still in your If the '''vm2nc''' machine.#Test email from command is not installed on your vm2 machine by sending an email to your , install it (install '''Seneca email accountnc''' using the following command:<br>for your '''mail -s "Lab4a - test1" <Your Seneca email address>vm3'''<br><br>as well).# Connect from your '''NOTE:vm2''' after you type in the body of the mail message, move to an empty line, type period "." and press itself using the ENTER key to send '''nc''' command by issuing the message.following command:<br><brsource >nc localhost 25</source>#Check your Seneca email account to You should see if you got the email (note that it may take a response: <ubr>few minutes to arrive<source >220 vm2.yourdomain.ops ESMTP Postfix</usource>, so you may also wish # You could theoretically use SMTP commands to try send an alternate email account if you have one like gmailhere, etc). When you do receive that email, make but this would be a note very unusual use 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. You have an '''MUA''' for a reason.#Test email from your Enter the command '''Host MachineQUIT''' by sending an email to your Seneca account using close the connection to the following command:server, then '''<brctrl>-c'''mail -r "hacker.com (Canadian Revenue Agency)" -s "Lab4a - test2" <Your Seneca email address>#Check your Seneca email to see if you got terminate the emailnc command. If you did, make a note of the return address. How would you think that including the  ::'''-rNOTE:''' option could be used by penetration hackers If it worked, this indicates that the postfix service is running, listening, and responding 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?connections.

<ol><li value===Testing email "4">Let's see if it works from other machines. Use '''nc''' to connect to '''vm2''' from '''vm3''' and see if it works. If your firewall is set up properly, the nc command should not permit a connection (i.e. ''no route to host'').</li><li>Create an iptables rule to allow incoming connections to your '''SMTP''' server on your '''vm2'''.</li><li>Once you open the port in the firewall, retry the '''nc''' command. You should get a different error this time (e.g. ''connection refused''). This time the problem is that your service isn't listening on the outside interface, it's currently configured to listen only on Local VM Machine the loopback (vm2lo)===interface.</li><li>Make sure the new iptables rule gets saved so that it will be loaded automatically from startup.</li></ol>

We will now test both your MUA (mailx) and MTA (postfix) by sending and receiving e-mail messages === Listening on the local VM2 machine only.all interfaces ===

'''Perform We need to configure the following Steps:'''MTA not only to listen to connections from other (separate) MTAs, but to set the domain name and server name in order to allow the user to issue emails in the "standard way", and allow mail messages to provide a correct email address for replies.

#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 the following command: '''cat /var/log/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?#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>#If you received an e-mail message, the message and subject line should appear as a listing in your mail command.<br>If you did not receive a mail message, check your mail server settings, check to see if you mail server is running and also check '''/var/log/messages'''.#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.#Re-issue the mail command. What happened?#Exit the mail command. Create a directory in your home directory called: '''mail'''.#Re-issue the mail command, and enter Perform the following command at the mail promptsteps: '''save 1 mail/msg1'''<br>Use the cat command to check the contents of '''/var/spool/mail<yourSenecaID>''' and '''~/mail/msg1'''. Exit the mail command.#Try sending another e-mail from your VM2 account to yourself, but using your first name instead by issuing the following command:<br>'''mail -s "Lab4a - Local - Test2" <yourFirstName>'''#Issue the '''mailq''' command on your VM2 machine (you will need to be root) to view the mail queue. Why would this command be useful for an administrator?#Now, issue the '''mail''' command to see if you received that e-mail message. Did it work? If so, why?<br>Record your observations in your OPS335 lab logbook.<br><br>#Finally, issue the following mail commands (using various e-mail addresses):<br>'''mail -s "Lab4a - Local - Test3" <yourSenecaID>.<vm2-IPADDR>'''<br>'''mail -s "Lab4a - Local - Test4" <yourFirstName>.<vm2-IPADDR>'''<br>'''mail -s "Lab4a - Local - Test5" <yourSenecaID>.vm2.<yourSenecaID>.org'''<br>'''mail -s "Lab4a - Local - Test6" <yourFirstName>.vm2.<yourSenecaID>.org'''<br><br>#Which of the following commands worked? Record your observations in your OPS335 lab logbook.

Arrange proof that Upon completion of this lab you can send e-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's sections=== You may choose to:* Submit screenshots of your work on Blackboard, in which case you don''VM2''' machine t need to come to the lab.* Or come to the lab, show me your '''Seneca College e-mail account'''work, and than talk to me about it. I want to hear what you can 've learned and answer any questions you have. You''send and receive e-mail messages locally on ll get the same grade regardless of how you choose to submit your VM2 machine only'''work.

#What does the term MTA mean? What is the purpose of an MTA?#What does the term MUA mean? What is the purpose of an MUA?#Briefly list the steps to install and configure your MTA on your server.#Briefly list the students to install the MUA on your server for text-based messaging.#Briefly list the steps to trouble-shoot your server if you could not send e-mail messages from your VM2 vm2 machine to an external e-mail server.#Write the command to send an e-mail message from your VM2 vm2 to your Seneca College e-mail account.#What are the commands to issue in the mail prompt to:<ul><li>Read the first e-mail message displayed</li><li>Save the 4th e-mail message to the file pathname: ~/maildir/3.msg.txt</li><li>Delete the 3rd e-mail message displayed</li><li>Exit the mail command prompt and return to the shell</li></ul><br>#What were the results of sending emails locally on your VM2 vm2 machine? Show log segments to verify your answers.# What is the purpose of an MTA?# What is the purpose of an MUA?# Draw a simple diagram showing how an MUA and an MTA are used to send e-mail messages between different servers.# List the steps to test a running postfix service using the nc application.