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You may not == OVERVIEW=={{Admon/important|Warning|Your lab 4a must be aware of it as a user but email is a very complex system to administer, in fact it's a very complex system of other archaic, hard-to-configure, sometimes-interoperable complex systemscomplete before you can start this lab.}}

WeIn Lab 4a, you configured and ran the 're going to spend three weeks working on it so that by the end of the course you will have ''Postfix''' application for our MTA (a general understanding of what services are involved in sending, filtering, and reading email. You will also have the skills to configure k.a basic setup using the default services . SMTP server) on CentOS 7your '''vm2''' and '''vm3''' machines.

== Overview ==That setup has some major drawbacks::* It required an SMTP server ('''MTA''') to be configured on each machine.:* The Message Store ('''MS''') would also be unique to each machine - what a user received on one server would not exist on any other.  In this lab you will centralize some of this information, so that a user can send email from any machine in the network, and have incoming mail sent to a centralized messages store. '''The a diagram below (duplicate to lab 4a) shows your basic setup of your email system:'''

You will begin by modifying the existing '''Postfix''' ('''MTA''') servers to make mail they send come from your domain (instead of each machine). Then you will add a record to your DNS server to allow mail to be sent to the domain itself, instead of the individual machines. Next, you will add a Local Delivery Agent ('''LDA''') to your '''vm3''' by installing '''dovecot-lda''', configure it, and test it to make sure that is is working correctly. Finally, you will set up an '''IMAP''' server called '''Dovecot''' on your '''vm3''' machine, so you can read your email from an MUA such as ''Thunderbird'' or a ''Webmail'' application. You will set up a webmail application called '''Roundcube''' in a later lab). === Learning About the Services Involved in an Email Delivery === In reality, the terms '''MTA''', '''MDA''', '''MUA''', '''LDA''' can actually be considered misleading since some of those services can be combined together to form a single entity (application), while other applications may operate as separate entities. There may be overlap, so if you don't find those acronyms helpful, don't worry too much about them. On the other hand, when referred to in diagrams, they can help to visualize those processes when trying to understand how an e-mail system works. [http://wiki.dovecot.org/MailServerOverview Here is an overview] of those terms (from the Dovecot wiki). It is worth viewing this link. In the diagram displayed above, the elements include: * '''User Account'''. The individual who wants to send or receive mail messages.* '''MUA''' (email client). This is the application that the individual uses to send or receive mail messages. It can be a '''native application''' or a '''web application'''. You will learn how to setup and use both types of these applications throughout the remainder of this course.* Two '''MTA''' servers. These are the servers responsible for getting your emails to the <u>destination</u> server.** They are similar to routers (which route packets) but work on the <u>application</u> layer rather than the <u>network</u> layer.** In our example, there are only two MTAs - but there can be several.** You connect to your MTA over a <u>secure</u> connection, so your emails can't be read by the operators of the network you're connected to.** The mail message then travels the rest of the way to the destination MTA <u>unencrypted</u>, so anyone with access to the routers in-between can read all your emails. That is why many organizations will refuse to send you confidential information over email.* '''LDA/MDA''' Server. This server will receive the email from the MTA, and will store it on disk in some format. '''MailDir''' and '''MBOX''' are the most popular mailbox formats.* '''IMAP/POP3''' server(s). When sending an email, you send it to the destination using your MTA, but you also want to save it in your '''"Sent"''' folder for yourself. This is accomplished by a separate connection to either your '''IMAP''' or '''POP3''' server.** Thus, a situation can occur that although you sent your email successfully, it may never make it to your "Sent" folder - the <u>second</u> connection to your IMAP server is quite unrelated to the first connection to the '''SMTP''' server.* '''DNS''' Server. A DNS server is also involved - it is needed to retrieve the address of the email server responsible for email for a particular domain. This is done with '''MX''' records. ===Online References=== * [Categoryhttps:OPS335//help.ubuntu.com/community/Dovecot Dovecot Community Documentation]* [http://wiki.dovecot.org/LDA Dovecot-lda]* [http://wiki.dovecot.org/LDA/Postfix Configuring dovecot-lda with postfix] == INVESTIGATION 1: INSTALL THUNDERBIRD (MUA) and SETUP A REFERENCE CLIENT== Unlike the '''mailx''' (MUA) application you installed and used in Lab 4a, this lab will be using the '''Thunderbird''' (MUA) application instead which is a graphical application that uses a '''centralized Message Store''' (MS) to retrieve and read mail messages.  Although we will be eventually setting up the Thunderbird application to perform all the mail operations discussed above, you need to learn to '''"walk before you can run"'''. Eventually, you are going to set up all those mail services, but to begin with, you will set up an email client to connect to an already working server which is the '''Seneca email server'''. Once we learn how to do this for our Seneca email account, then we can use it for our mail servers for our VM2 and VM3. '''Perform the following steps:''' #Switch to your '''host''' machine, and install the '''Thunderbird''' email application.#When you first launch the Thunderbird application, a configuration dialog should appear as shown in the diagram below: <br>::[[CategoryImage:OPS335 LabsSeneca-student-thunderbird-email-setup.png|600px]]<br><ol><li value="3">Use the data in the table below to configure the Thunderbird settings dialog box for YOUR Seneca e-mail account:</li></ol>

The diagram above doesn{| class="wikitable" border="1" style="margin-left:40px;"! Setting !! '''Incoming: IMAP''' !! '''Outgoing: SMTP'''|-| '''Username''t even include reading email, but it's as simple as it gets (if you want to run an email server)|| yoursenecauserid@myseneca. You will need to learn to administer basics of all the systems in the diagramca || yoursenecauserid@myseneca. We wonca|-| '''t go in too much depth, only the minimum you needservername''' || outlook. But we will not (for example) go over every detail of Postfix, which on its own has a rather office365.com || outlook.office365.com|-| '''port''' || 993 || 587|-| '''security''' || SSL/TLS || STARTTLS|-| '''References''' | colspan="2" | [1] [https://enemployees.wikipediasenecacollege.orgca/wikispaces/77/Postfix_%28software%29#Architecture complex] [https:it-services/wiki/www.credativ.deview/blog2394/postfixother-email-architectureclients ITS -overview diagramConfiguring other Email Clients].|}

=== Services involved in ::Note that your username is your full email delivery ===address(<em>yourid@myseneca.ca</em>) and not just <em>yourid</em>.

[http:{{Admon/important |Unencrypted Options|Notice that there are <u>unencrypted</u> options available to connect to your SMTP/IMAP servers but those are rarely used these days - the potential for abuse is too great. On a free wifi network, the operator would be able to not only read your email, but also obtain your password without any password/wikiencryption cracking tools.dovecotIn fact, even on a private wired network, it is not uncommon for an employer to use a packet sniffer utility to monitor all the traffic going over their network (Packet Sniffing applications were actually found to be legally acceptable practice if used by the management of organizations)}}<br><ol><li value="3">After you create your '''Thunderbird''' account, you should be able to read your existing email and send new email within the Thunderbird application.org</MailServerOverview Hereli><li>Take time to view your 's an overview] 'Account Settings'' and ''Preferences'' to get a feel for what settings exist. For example:<ul><li>How often will Thunderbird check for new messages?</li><li>Will the messages you write be in HTML or plain text?</li><li>How do you change your SMTP server settings? Why are they in a different section?</li></ul></li><li>The main objective of from this section was to learn how to setup your Thunderbird application to read your Seneca email, so in the Dovecot wiki, it's worth readingnext section you can use the exact type of setup for your own email server.</li></ol>

* == INVESTIGATION 2: SETUP A user. That's the person who wants to send an email.* An MUA (email client). This is the application the user uses to send an email. It can be a native application or a web application. We'll set up both types.* Two MTAs. These are the servers responsible for getting your emails to the destination server.** They are similar to routers (whcih route packets) but work on the application layer rather than the network layer.** In our example there are only two MTAs - but there can be several.** You connect to your MTA over a secure connection, so your emails can't be read by the operators of the network you're connected to.** The rest of the way to the destination MTA the emails travel completely unencrypted, so anyone with access to the routers in between can read all your emails. This is why many organizations will refuse to send you confidential information over email.* The LDA/MDA will receive the email from the MTA, and will store it on disk in some format. MailDir and MBOX are the most popular mailbox formats.* When sending an email you send it to the destination using your MTA, but you also want to save it in your "Sent" folder for yourself. This is accomplished by a separate connection to your IMAP or POP3 server.** This is why it can happen that you sent your email successfully but it never makes it to your "Sent" folder - the second connection to your IMAP server is quite unrelated to the first connection to the SMTP server.* Note that a DNS server is also involved - it's needed to retrieve the address of the email server responsible for email for a particular domain. This is done with the MX records we looked at in the DNS labs.CENTRALIZED MESSAGE STORE ==

== Sample client setup = Setup Your MTA to Use Correct Domain===

Eventually we're going In Lab 4a, both of your email servers were sending mail messages addressed from users of the actual machines themselves. This would be confusing for the receiver who might get emails from the same user @vm1, vm2, and vm3. Which would they respond to set up all those services? To avoid this problem from occurring, but to begin with we'll set up an email client to connect can make all servers make the sent mail appear to come from a central location (hopefullyusually the '''domain''') working server - the Seneca , and make incoming email server. This will sent to that address to be a good exercise with an email clientaccessible from machines within our network.

Install Thunderbird on your host, and configure it like this, obviously using your own information'''Perform the following steps:'''

[[Image:Seneca-student-thunderbird-# Issue the '''mail''' command to view the email-setupmessages you sent between your '''vm2''' and '''vm3''' in your lab 4a. Notice that each is addressed from root on whichever machine sent it.# On both machines (vm2 and vm3), edit the '''/etc/postfix/main.cf''' file to change the '''myorigin''' parameter from '''$myhostname''' to '''$mydomain'''. Restart the '''postfix''' service.# Now, send emails messages (via the '''mail''' command) between both of your vm2 and vm3 machines, and view the mail messages by issuing '''mail''' in each vm. The sender address should now read that the received mail messages came from '''root@yourdomain.ops'''.png|600px]]

::The specific security settings depend on how your servers were configured. The settings for next step is to configure what addresses that the seneca servers are [https://inside.senecacollege.ca/its/services/server will receive email/email_clients/imapfor.html published here] This is done using postfix by setting the '''mydestination''' parameter (configuration variable) to include '''$mydomain''' (this is assuming you've set up '''mydomain''', '''myorigin''' , and '''inet_interfaces''' properly).

Look through <ol><li value="4">Edit the Account Settings '''/etc/postfix/main.cf''' file for '''vm3 ONLY''', scroll down to the line containing: '''mydestination''' and Preferences change line to get a feel for what settings existthe text shown below:<br><source>mydestination = $mydomain, $myhostname, localhost.$mydomain, localhost</source>'''Note:''' Even though your machine's name is ''vm3.yoursenecaid. For exampleops'', your postfix MTA will also receive emails addressed to the domain called:yoursenecaid.ops</li></ol>* How often <br>::In order for this to work, we need to add a DNS record that will Thunderbird check for new messages?* Will point mail sent to the domain towards one of the messages you write be in HTML or plain text?* How do you change your SMTP server settings? Why are they in a different section?servers configured to accept it.

If everything is working - that<ol><li value="5">Add an '''MX''' record to the forward lookup zone on '''host''s good, now you know what you'll try so that all incoming mail addressed to build in the email labs. The goal domain is sent to have your vm3.</li><li>Restart the exact same setup using service and use the '''dig''' command to confirm that it works.</li><li>Send an email from your servers instead of Seneca servers'''vm2''' to '''root@yourdomain.ops'''</li><li>Confirm that it arrives on your '''vm3''' machine</li></ol>

= MTA for sending (no encryption) == Relay Email Through Another Server===

We'll use Postfix as When email is sent from either vm, it is addressed from the MTAdomain, and we'll set it up on '''but receiving MTAs might query why mail sent from vm2doesn'''. This will be t match the email server for your internal network. You'll be able to send email out address of your network, and receive email from within your network, but not receive from outside your network because:# Outsiders will never find the MX recors record for your the domain, because there are no .org servers pointing to your DNS server (you haven't paid This would be a red-flag for it)potential spam.# Even if they did - your local To avoid this, we can relay all mail sent from vm2 (or any other machine in our network is using IP addresses on a private subnet, which is not routeable on the internet, ) through vm3 so that it cannot be reached properly appears to come from the outsidemail server that matches the MX record for the domain.

Postfix should be installed by default. If it isn't - go ahead and install it. Install also ''Perform the netstat application (use yum search to find the package name) and the telnet command.following steps:'''

Postfix will work with # Move to your vm2 machine.# Direct your '''vm2''' MTA to relay mail through vm3, by making the following editing change for the '''/etc/postfix/main.cf''' file:<br><source>relayhost = vm3.<yourdomain>.ops</source># Restart the default configuration'''postfix''' service.# Next, so enable it, start it, and check that you must instruct your '''vm3''' machine to allow your vm2 machine to pass email through itby making the following editing change to the '''/etc/postfix/main.cf'''s runningfile:<br><source>mynetworks = 192.168.X. Also look 0/24</source>NOTE: Substitute in your '''own network''' for it in X<br><br># Restart the list of listening ports:'''postfix''' service.

Which one is it? Find the port used by SMTP, === Install and look for connctions with Configure the state LISTEN Local Delivery Agent (i.e. currently listeningLDA/MDA).===

== Testing Postfix is capable of performing the connection to function of an LDA, but its LDA capabilities are limited, thus postfix is generally not used for that purpose. Currently, the most popular LDA is ''LMTP'', but we will be installing, configuring, and using an LDA called '''Dovecot''' since it is also popular and we will setting up Dovecot as an '''IMAP''' server later in this lab. Using both Postfix ==and Dovecot will actually increase the performance of our IMAP server.

Connect from your server to your server using telnet'''Perform the following steps:'''

#Move to your '''vm3''' machine.#Dovecot is not installed when you installed your Virtual machines in previous labs.<br>Install the Dovecot application by issuing the following command:<br><source>yum install dovecot</source>#Edit your '''/etc/postfix/main.cf''' file and scroll down to (or search for) '''mailbox_command'''. Add the following line:<br><source lang>mailbox_command =/usr/libexec/dovecot/dovecot-lda -f "$SENDER" -a "bash$RECIPIENT">telnet localhost 25</source>

Note that ::NOTE: Do <u>'''not'''</u> replace any variables, those are set automatically by Postfix when it will tell runs the LDA. If you are interested in learning more about the Dovecot application, you once your connect that can read about dovecot-lda [http://wiki.dovecot.org/LDA/Postfix here] and [http://wiki.dovecot.org/LDA here].<br><ol><li value="4">Finally, edit the '''Escape character is /etc/dovecot/conf.d/10-mail.conf'^]''', which means file and indicate where you want your mail delivered by including the following line:<source>mail_location = maildir:~/Maildir</source></li><li>Restart your can hold control and press postfix service.</li><li>While the square bracket key emails are still stored only on VM3, they will now be easier for other machines/services to access.</li><li>Due to end permissions on the session (and then exit directories where mail will now be stored, root will no longer receive mail. Check the telnet app)logs for an indication as to why.</li></ol>

If this worked - that means the service is running and listening and responding to connections. Let's see if it works from other machines. Telnet to vm2 from the host (connect to the SMTP port) ''Record steps, commands, and see if it works. If your firewall is set up properly observations in INVESTIGATION 2 in your OPS335 lab log- it shouldnbook''t, you'll need to allow incomming connections to TCP port 25.

Once you open the port in the firewall - try the telnet command. You should get a different error this time. This time the problem is that your service isn't listening on the outside interface, it's currently configured to listen only on the loopback ==INVESTIGATION 3: USING THUNDERBIRD (loMUA) interface.FOR VM2 and VM3 MACHINES ==

== Listen = Accessing Received Mail Messages on all interfaces VM3 VIA IMAP ===

First, we will set up the IMAP server so we can read email. The first change current way we have configured our mail server on our VM3 machine should allow all the email for anyaccount@yoursenecaid.ops should be delivered to the Postfix configuration our '''vm3''' machine. We will be set up Dovecot with IMAP to get easy access to make it listen for incoming connections on the extrnal intercace, that's eth0 from the VMs point of viewemail.

The configuration file is '''/etc/postfix/main.cfPerform the following steps:''' Edit it and change '''inet_interfaces''' to '''all'''.

Restart postfix, confirm #The configuration file for the Dovecot service (with netstatwhich is not the same thing as dovecot-lda) is: '''/etc/dovecot/dovecot.conf'''. Modify the '''protocols''' option so that Dovecot will work with IMAP connections, no POP3 or LMTP.# Start the dovecot service, and ensure itwill always start automatically when the machine boots.# Use the 's now ''ss''' command to confirm the service is listening , and use '''nc''' on the '''host''' to confirm you can connect to it.# You'll probably fail, so using the information gathered from '''ss''', modify the firewall on all interfacesvm3 to allow IMAP connections from your local network and try '''nc''' again. Once it works, do not just loopbackforget to save this change so it will still be there the next time you reboot.#If you can connect - it's now time to do something wrong, that is allow connections to our IMAP server over an unencrypted connection.# Edit the '''/etc/dovecot/conf.d/10-auth.conf''' file and test connecting set '''disable_plaintext_auth''' to it from '''no'''.# Then edit the '''/etc/dovecot/conf.d/10-ssl.conf''' file and set '''ssl''' to '''yes'''.<br><br>'''Note:''' This combination of parameters will allow your username and password to be sent over the internet in plain text, for anyone interested to look at. In a later lab we'll set up secure SMTP and IMAP connections, for now this is all we have time for.<br><br># Restart dovecot so the hostchanges take effect.

== Setup = Connecting to IMAP Servers Using Thunderbird ===

The process is a little challenging because Thunderbird tries really hard #On your '''host''' machine, return to prevent you from connecting to a server that doesn't work the Mail Account Setup dialog box (and ours mostly doesn't work at this pointeg. near top of lab). # Set it up a '''new email account'''. You will be using account settings to connect to your IP address (192.168.X.3) '''vm2''' for '''SMTP''' and '''vm3''' for both '''IMAP and SMTP'''. Use <u>no </u> encryption, and use normal password authentication for IMAP (we don't have an IMAP server running yet, but that's ok).Refer to the diagram below for reference:

<ol><li value="3">Try to connect to your IMAP server with Thunderbird by clicking on your '''Inbox'''.</li><li>If nothing happens, then check the Thunderbird wonActivity Manager for any errors. If the connection is successful, you should see the '''Trash''' box <u>appear</u> below Inbox.</li><li>Use the Thunderbird application to send an email to your myseneca address. If you've done everything right, it will send the message successfully</li><li>Verify that your message has been sent. Check your myseneca email and look at '''/var/log/maillog''' on vm2 (your email server).</li></ol> === Sending a Mail Message from VM2 (Using Thunderbird)=== '''Perform the following steps:''' #Use the '''ss''' and '''nc''' commands (like you did in lab 4a) to confirm your service is listening on the correct ports/interfaces. You will probably have to open the appropriate firewall port on '''vm3''' to allow incoming '''SMTP''' connections.<br><br>'''Note:''' You should be able to send email to any regular user <u>on</u> '''vm3''' using the email address '''yourusername@yoursenecaid.ops''' using the Thunderbird application on your host machine (which is configured to use the account on your vm2).<br><br> <ol><li value="2">Create a new account on your '''vm3''' machine using only your <u>first</u> name. We will use this account as a one-time "test" if the mail message has been received on your VM3 machine (from your VM2 machine).<br><br>'''Note:''' It is <u>'''important'''</u> that you '''<u>don't let </u>''' create this same account name on your vm2 machine, since you proceed with want to easily identify the difference between the sending and receiving SMTP servers.<br /><br /></li></ol> <ol><li value="Done3" button because >Use the new account in Thunderbird to send an email to '''firstname@yoursenecaid.ops''' and then check the contents of '''/home/firstname/Maildir/new/''' on your '''vm3''' machine. There should be a file there with the contents of your email.</li><li>If there is no file, then check the log file '''/var/log/maillog''' to see what went wrong.</li><li>If you can see a file in the '''/home/firstname/Maildir/new/''' directory, then review the procedures on how you will fail got the email server working (since you have performed many steps and set up many services).</li><li>Refer to the diagram at the top of this lab. Which services have you currently set up? Record your findings in your lab Logbook.</li></ol> {{Admon/important |Encountering error messages when sending email|If you cannot properly receive sent e-mail messages, check the '''/var/log/syslog''' file for errors.<br><br> If you locate an error message in that file such as: '''Fatal: Error reading configuration: Invalid settings...''', then add the following <u>parameter</u> in '''/etc/dovecot/dovecot.conf''':<br />'''postmaster_address <nowiki>=</nowiki> DOMAIN''' (where DOMAIN is actually <u>your</u> domain).<br /><br />After you have saved those changes, then '''restart''' your dovecot service. This problem can also be resolved by properly setting the hostname of your machine to include the domain.}} {{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.}} '''Record steps, commands, and your observations in INVESTIGATION 3 in your OPS335 lab log-book''' == COMPLETING THE LAB == ===Online Submission===Follow the instructions for lab 4b on blackboard.<!--===Andrew's sections=== You may choose to:* Submit screenshots of your work on Blackboard, in which case you don't need to come to the lab.* Or come to the lab, show me your work, and talk to connect me about it. I want to IMAPhear what you've learned and answer any questions you have. Use  You'll get the same grade regardless of how you choose to submit your work. ::<span style="Advanced configcolor:green;font-size:1.5em;" button >&#x2713;</span>Status and configuration of your Postfix service on vm2.::<span style="color:green;font-size:1.5em;">&#x2713;</span>Proof that you can connect to bypass that checkservice from the host.::<span style="color:green;font-size:1.5em;">&#x2713;</span>Your Thunderbird configuration.::<span style="color:green;font-size:1.5em;">&#x2713;</span>The email you sent to your myseneca account.::<span style="color:green;font-size:1.5em;">&#x2713;</span>Download and run '''wget https://ict.senecacollege.ca/~andrew.smith/ops335/labcheck4b.bash''' on your '''c7host''' machine. ::<span style="color:green;font-size:1.5em;">&#x2713;</span>Completed Lab4b log-book notes.--> ==EXPLORATION QUESTIONS== # What is the purpose of the Thunderbird application?# List the steps to configure your DNS to allow your Thunderbird application to connect to your mail server.# What is the purpose of the '''Dovecot''' package?# What is the purpose of the '''mydestination''' parameter contained in the '''/etc/postfix/main.cf''' file?# Why are '''IMAP''' and '''POP''' email servers placed on separate machines (vms)?# What is the purpose of the '''mail_location''' parameter contained in the '''/etc/dovecot/conf.d/10-mail.conf''' file?# Why is root not able to receive mail with the changed mail location? What could you change to allow mail to be sent to root again?