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When someone tries to send email to '''senecacollege.ca''' - they actually want to send email to the Seneca * [ OPS335 Mail Server Notes ] Course Note providing Concepts and Overview of mail server, which is not senecacollegesetup* [http://www.cafredshack. That is a very typical com/docs/postfix.html Postfix for Dummies] Good Basic Guide to setup for any business - it simplifies administration and helps a little with load balancing.Postfix MTA

<source lang="bash">dig senecacollege=OVERVIEW &amp; PREPARATION==This lab will show you how to set up a '''Postfix''' email server ('''MTA''') on your '''VM2''' and '''VM3''' machines. You will also be setting up on your '''VM2''' and '''VM3''' machines the '''mailx''' package ('''MUA''') to allow users to send and receive text-based mail messages. You should also be able to send email messages to your Seneca College email account.ca MX</source>

Notice that The diagram below shows the email servers aren't even a subdomain layout of senecacollege.ca but a completely different company (Microsoft in the what this case). In other cases (for example check the records for google.com) the email servers are within the company's domain.lab should be able to accomplish:

Notice that the response for your dig commainds for MX records contains domain names and not IP addresses. That means that when you look for a domain's [[Image:email server - you may need to do a query for MX and another for Asetup.png]]

== CNAME record INVESTIGATION 1: INSTALL &amp; SETUP THE MAIL TRANSFER AGENT (MTA)==

Sometimes you want multiple domain names {{Admon/important|Prerequistites|<ol><li>Ensure <u>all</u> machines have been updated and that the '''clocks are set to point the correct date and time'''.<br></li><li>Due to the same changes made in this lab3, '''you will now need your vm1 running (as the DNS server. The most common example )''' in order for any of this is the www. subdomain. Use dig your virtual machines to be able to find use the main web server for Seneca or for CBCinternet.</li></ol>}}

A TXT record can store pretty much anything, it's typically used for purposes that ''Perform the desiners of DNS havenfollowing steps:'''t though of themselves. For example a common use of a TXT record is SPF: a record that helps receiving email servers to determine the likelyhood that a message is spam.

Configure at least one of each of the records above for your domain served by the Bind server in your vm1 ===Install and verify that your records work.configure Postfix on a VM===

How much detail goes into #Switch to your '''VM2''' machine.#Check the test plan depends on status of the resources available for testing, '''sendmail''' service by using the scale of '''systemctl''' command. If the changessendmail service is running, use the systemctl command to stop and disable that service. #Issue the following command to install the '''Postfix''' application (MTA):<br><br>'''yum install postfix'''<br><br>#What is the purpose of installing the risk associated with getting things wrongpostfix application in terms of using e-mail? Record your answer in your lab logbook. In your case <br><br>'''NOTE:''' We need to configure the worst postfix application (i.e. our MTA) to recognize our recently-created domain name thatwe setup in lab3.<br><br>#Edit the Postfix configuration file: '''/etc/postfix/main.cf''' and edit this file to contain only the contents displayed below:<br><br>'''mydomain = senecaID.org'''<br>'''myorigin = $mydomain'''<br>'''mynetworks = 127.0.0.0/8, 192.168.X.0/24'''<br>'''relay_domains ='s going ''<br>'''inet_interfaces=all'''<br><br>'''NOTE:''' Your MTA has the ability to resolve "fake" public address to happen an actual user account name. For example, if you misconfigure have a server user account called "msaul", you can have the MTA resolve the fake name "murray.saul" to the account name "msaul".<br>In order to do this you need to create an alias which is youcontained in the MTA'll lose some markss alias file. <br><br>#Edit the '''/etc/postfix/aliases''' file and add your first name as an alias to be resolved to your VM2's account name:<br><br>'''your-first-name''' &nbsp; &nbsp; &nbsp; '''your-vm2-regular-username'''<br><br>#In order to update the MTA's database for the newly-create alias, issue the following command:<br>'''postalias hash:/etc/aliases'''<br><br>#Finally, to start and enable your MTA, issue the following commands:<br><br>'''systemctl start postfix.service'''<br>'''systemctl enable postfix.service'''<br><br>#Check the industry a mistake like '''/var/log/messages''' file to see that can cost the company you work for a lot of money (perhaps even more than your salary)MTA server started without error If there are any errors, correct them before continuing.

Generally speaking each test case typically has at least one expected positive and some number of expected negative results. For example if you're setting up a DNS record for www.yoursenecaid.org your test case might look something like this==INVESTIGATION 2:INSTALL &amp; SETUP THE MAIL USER AGENT (MUA)==

[[Image:Sample_test_caseWe will be using a simple text-based Mail User Agent called mailx to send messages between your running mail servers (MTAs).png|800px| ]]

You can spend an infinite amount of time running tests and stil not prove anything definitively, so you have to do your best to make sure === Installing the tests you run are representative of the requirements - that after a successful run of all the tests the service is almost certainly working correctly.Mail User Agent (MUA)===

Test cases #Issue the following command to install the '''mailx''' application (in a test suite, in a system that keeps track of themMUA) are not intended :<br><br>'''yum install mailx'''<br><br>#Refer to only show that the system is working. It's equally valuable chart below to acquaint yourself on how to see that at some point in use the past there was a problem. In that case there may be a bug number or some other means of tracking down what caused the problem in the past and how it was fixed. So recording failed test results is just as important as recording passes.mailx application:

Pick any section of any lab you like that would justify having at least three test cases. Write ===Testing mail with the test cases in a template, save a copy of that for the current test run, and execute the tests, recording the results.internet===

To submit '''Perform the following steps:''' #Test email from your machine by sending an email to your Seneca account using the following command:<br><br>'''mail -s "PART C3" <Your Seneca email address>'''<br><br>'''NOTE:''' after you type in your letter, enter a period in the first column on the last line and hit the ENTER key.<br><br>#Check your learn email to see if you got the email (note that it may take a few minutes to arrive, so you may also wish to try an alternate email account if you have one). 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 machine to determine what the error is.#Test email from your Host Machine by sending an email to your Seneca account using the following command:<br><br>'''mail -s "PART C4" -r hacker@evil.com <Your Seneca email address>'''<br><br>#Check your Seneca email to see if you got the email. If you did make a note of the return address.#Repeat the steps for INSTALL &amp; '''SETUP THE MAIL TRANSFER AGENT (MTA)''' and '''INSTALL &amp; SETUP THE MAIL USER AGENT (MUA)''' for your '''VM3'''. ===Testing email using IP Addresses=== If you were able to send e-mail to your Seneca e-mail account from your VM2 and VM3, then we should test to see if we can send email messages within our virtual private network.First, let's send a message using a static IP ADDRESS for each VM: '''Perform the following Steps:''' #Adjust your firewall (iptables) to allow traffic to port 25 on both VMs.# Check your '''/var/log/maillog''' file to see the log entries get created when mail is sent and received, or notes when something goes wrong.#Try sending an email from '''vm2''' to your '''vm3''' by issuing the command:<br><br>'''mail -s "PART E2" yyyyyy@[192.168.X.4]'''<br><br>#Try sending an email from your '''vm3''' to '''vm2''' by issuing the command:<br><br>'''mail -s "PART E3" root@[192.168.X.3]''' <br><br> ===Test email using host names=== Let's complete this lab by sending email messages using our recently- show created domain name: '''Perform the following Steps:''' #Use the '''host''' and '''hostname''' commands to confirm that each of your machines has the same ''hostname'' and that the new DNS records service verifies this to be true.#Restart your MTA (postfix) server if you changed the hostname on either mail server.#Try sending mail to yourself on both machines. For example, as the username <senecaID> on VM 3, use the command:<br><br>$ mail <senecaID>@vm2.<yourdomain>.org<br><br>'''NOTE:''' the machine will prompt for a subject: enter "testing" without the quotes.<br><br>#Enter the body of your e-mail message. When you have completed entering your email message, enter a period (.) in column 1 on the last line of your letter. This will send the signal: '''end-of-file''' and your letter will be mailed. You should end up back at the shell prompt. If you make a mistake, use '''CTRL-C''' to cancel the email (DO <u>NOT</u> USE CTRL-Z).#Use the '''mailq''' command on both machines (you will need to be root) to view the mail queue. Why would this command be useful for an administrator?#Use the mail command to check to see if you created are served correctly have received any mail. '''Record steps, commands, and your observations in INVESTIGATION 2 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 VM 2 to VM 3, and from VM 3 to VM 2), and show to your seneca email (or other external mail server).  ==EXPLORATION QUESTIONS== #What did changing the relay_domains parameter do?#What firewall rule or rules, if any, did you have to enter so that email between your VMs would work?#What is the meaning of the square brackets surrounding the IP address in the examples?#What were the results of sending email between the VMs? Show log segments to verify your completed test plananswers.