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= Email Servers = You may not be aware of it as an user, but email is a very <u>complex</u> system to administer. In fact, the more modern e-mail systems (eg. web-based mail applications, etc) are more technically involved than the other archaic, hard-to-configure, and sometimes inter-operable mail systems. 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.[[Category:OPS335]][[Category:OPS335 Labs]]

==LAB RESOURCESOVERVIEW=={{Admon/important|Warning|Your lab 4a must be complete before you can start this lab.}}

That setup has some major drawbacks::* [http://wiki.dovecot.org/MailServerOverview Here's It required an overview] SMTP server (common mail server terms'''MTA''')to be configured on each machine.:* [https://inside.senecacollege.ca/its/services/email/email_clients/imap.html Seneca Client Settings] The Message Store (Seneca Server settings for mail client '''MS''') would also be unique to each machine - Thunderbird) what a user received on one server would not exist on any other.

In factFinally, the above diagram does not include reading mail messagesyou will set up an '''IMAP''' server called '''Dovecot''' on your '''vm3''' machine, but this acts so you can read your email from an MUA such as ''Thunderbird'' or a starting point in order to run a basic email server''Webmail'' application. Although You will be learning to administer the mail services set up a webmail application called '''Roundcube''' in the diagram above, we will not required you to go into tremendous depth (just the minimum requirementsa later lab). 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].

=== Learning About the Services involved Involved in email delivery 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 try trying to understand how an e-mail system works.

[http://wiki.dovecot.org/MailServerOverview Here's is an overview] of those terms (from the Dovecot wiki). It is worth viewing this link.

* A '''userUser Account'''. That's the person The individual who wants to send an emailor receive mail messages.* An '''MUA''' (email client). This is the application that the user individual uses to send an emailor receive mail messages. It can be a '''native application ''' or a '''web application'''. We'll set up You will learn how to setup and use both typesof these applications throughout the remainder of this course.* Two '''MTAsMTA'''servers. These are the servers responsible for getting your emails to the <u>destination</u> server.

* The '''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.

* Note that a '''DNS''' Server. A DNS server is also involved - it is needed to retrieve the address of the email server responsible for an email for a particular domain. This is done with the '''MX ''' records . ===Online References=== * [https://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 looked at 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 DNS labsdiagram below: <br>::[[Image:Seneca-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>

{| class="wikitable" border="1" style= Install Thunderbird Application and Setup a Reference Client =="margin-left:40px;"! Setting !! '''Incoming: IMAP''' !! '''Outgoing: SMTP'''|-| '''Username'''|| yoursenecauserid@myseneca.ca || yoursenecauserid@myseneca.ca|-| '''servername''' || outlook.office365.com || outlook.office365.com|-| '''port''' || 993 || 587|-| '''security''' || SSL/TLS || STARTTLS|-| '''References''' | colspan="2" | [1] [https://employees.senecacollege.ca/spaces/77/it-services/wiki/view/2394/other-email-clients ITS - Configuring other Email Clients]|}

Eventually we're going to set up all those mail services, but to begin with, we will set up an ::Note that your username is your full email client to connect to a address(hopefully<em>yourid@myseneca.ca</em>) working server - the Seneca email server. This will be a good exercise with an email clientand not just <em>yourid</em>.

When you see {{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 configuration dialog boxoperator would be able to not only read your email, but also obtain your password without any password/encryption cracking tools. In fact, even on a private wired network, configure it in is not uncommon for an employer to use a similar way 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'''using account, you should be able to read your existing email and send new email within the Thunderbird application.</li><li>Take time to view your own information'') as shown 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 this section was to learn how to setup your Thunderbird application to read your Seneca email, so in the diagram below:next section you can use the exact type of setup for your own email server.</li></ol>

[[Image:Seneca'''Record steps, commands, and your observations in INVESTIGATION 1 in your OPS335 lab log-student-thunderbird-email-setup.png|600px]]book'''

After you create 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? To avoid this problem from occurring, we can make all servers make the sent mail appear to come from a central location (usually the '''Thunderbirddomain''' account), you should be able to read your existing email and send new make incoming email sent to that address to be accessible from machines within the Thunderbird applicationour network.

Take time to view your ''Account Settings'' and 'Perform the following steps:'Preferences'' to get a feel for what settings exist. For example:* How often will Thunderbird check for new messages?* Will 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?

The main objective of this section was # Issue the '''mail''' command to learn how to setup view the email messages you sent between your Thunderbird application to read '''vm2''' and '''vm3''' in your Seneca emaillab 4a. Notice that each is addressed from root on whichever machine sent it.# On both machines (vm2 and vm3), so in edit the '''/etc/postfix/main.cf''' file to change the '''myorigin''' parameter from '''$myhostname''' to '''$mydomain'''. Restart the next section you can use '''postfix''' service.# Now, send emails messages (via the exact type '''mail''' command) between both of setup for your own email servervm2 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'''.

We be ::The next step is to configure what addresses that the server will receive email for. This is done using postfix by setting the '''Postfixmydestination''' application as the parameter (configuration variable) to include '''MTA$mydomain''', and we will be setting it (this is assuming you've set up on your '''vm2mydomain''' machine. This will act as the email server for your internal network. You will be able to send email out of your network, and receive email from within your network, but you will '''<u>not</u>myorigin''' 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 , and '''.orginet_interfaces''' servers pointing to your DNS server (i.e. you haven't paid for itproperly).# Even if they the individuals could read your MX records, your local network is using IP addresses on a '''private subnet''', which is not routeable on the Internet, so it cannot be reached from outside of your system.

Perform <ol><li value="4">Edit the following steps'''/etc/postfix/main.cf''' file for '''vm3 ONLY''', scroll down to the line containing: '''mydestination''' and change line to the text shown below:<br><source>mydestination = $mydomain, $myhostname, localhost.$mydomain, localhost</source>'''Note:''' Even though your machine's name is ''vm3.yoursenecaid.ops'', your postfix MTA will also receive emails addressed to the domain called:yoursenecaid.ops</li></ol><br>::In order for this to work, we need to add a DNS record that will point mail sent to the domain towards one of the SMTP servers configured to accept it.

#The <ol><li value="5">Add an '''postfixMX''' application should be installed by default. If it isn't, install it.#Install also record to the forward lookup zone on '''netstathost''' application (tip: use yum search so that all incoming mail addressed to find the package name) domain is sent to your vm3.</li><li>Restart the service and also install use the '''telnetdig''' command.#Postfix will work with the default configuration, so start and enable this service, and verify to confirm that the postfix service is runningit works.#Look for the running postfix service in the list of listening ports by issuing the following command:<br/li><source lang="bash"li>netstat -atnpSend an email from your '''vm2''' to '''root@yourdomain.ops'''</sourceli>#Which service is postfix running? Locate the port used by SMTP, and look for connctions with the state LISTEN (i.e. currently listening).#Write <li>Confirm that it arrives on your observations in your lab logbook.'''vm3''' machine</li></ol>

=== Testing the connection to Postfix Relay Email Through Another Server===

Connect When email is sent from your server either vm, it is addressed from the domain, but receiving MTAs might query why mail sent from vm2 doesn't match the address of the MX record for the domain. This would be a red-flag for potential spam. To avoid this, we can relay all mail sent from vm2 (or any other machine in our network) through vm3 so that it properly appears to your come from the mail server using telnet:that matches the MX record for the domain.

Note that it will tell you once # Move to your vm2 machine.# Direct your connect that '''Escape character is 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 '''postfix''' service.# Next, which means you must instruct your '''vm3''' machine to allow your can hold control and press vm2 machine to pass email through it by making the square bracket key following editing change to end the session (and then exit '''/etc/postfix/main.cf''' file:<br><source>mynetworks = 192.168.X.0/24</source>NOTE: Substitute in your '''own network''' for X<br><br># Restart the telnet app)'''postfix''' service.

If this worked - that means the service All mail is running and listening now being delivered to a centralized location (and responding also appears to connections. Let's see if it works be coming from other machines. Telnet to vm2 from the host (connect to the SMTP portthat same location) and see if it works. If your firewall is set up properly - it shouldn't, you'll need but a user would still have to allow incomming connections access that server to TCP port 25retrieve it.

Once you open === Install and Configure 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 Local Delivery Agent (loLDA/MDA) interface.===

The first change to '''Perform the Postfix configuration will be to make it listen for incoming connections on the extrnal intercace, thatfollowing steps:'''s eth0 from the VMs point of view.

The configuration file #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''' Edit it file and change '''inet_interfaces''' scroll down to (or search for) '''allmailbox_command'''.Add the following line:<br><source>mailbox_command = /usr/libexec/dovecot/dovecot-lda -f "$SENDER" -a "$RECIPIENT"</source>

At this point we should also set the string that will end up in the ::NOTE: Do <u>'''From:not''' header </u> replace any variables, those are set automatically by Postfix when it runs the LDA. If you are interested in messages sent by this serverlearning more about the Dovecot application, you can read about dovecot-lda [http://wiki.dovecot.org/LDA/Postfix here] and [http://wiki.dovecot.org/LDA here]. Change <br><ol><li value="4">Finally, edit the '''mydomain/etc/dovecot/conf.d/10-mail.conf''' file and indicate where you want your mail delivered by including the following line:<source>mail_location = maildir:~/Maildir</source></li><li>Restart your postfix service.</li><li>While the emails are still stored only on VM3, they will now be easier for other machines/services to access.</li><li>Due to your domain name and and '''myorigin''' permissions on the directories where mail will now be stored, root will no longer receive mail. Check the logs for an indication as to '''$mydomain'''why.</li></ol>

Restart postfix, confirm (with netstat) that it's now listening on all interfaces''Record steps, not just loopbackcommands, and test connecting to it from the host.your observations in INVESTIGATION 2 in your OPS335 lab log-book'''

=== DNS Server used by the host =INVESTIGATION 3: USING THUNDERBIRD (MUA) FOR VM2 and VM3 MACHINES ==

Modify your /etc/resolv.conf to use vm1 as First, we will set up the name IMAP serverso we can read email. This will not be a permanent change but that's ok, The current way we only need it for have configured our mail server on our VM3 machine should allow all the email labsfor anyaccount@yoursenecaid. Youops should be delivered to our '''vm3'''ll have machine. We will set up Dovecot with IMAP to remember get easy access to do this every time you reboot your hostthat email.

If you regular (internet) DNS lookups slow down significantly - try to update '''Perform the DNS server configuration on vm1 to forward requests to the Google nameserver (8.8.8.8) instead of your host.following steps:'''

==INVESTIGATION 2#The configuration file for the Dovecot service (which is not the same thing as dovecot-lda) is: SETUP THUNDERBIRD MUA FOR YOUR VIRTUAL NETWORK (vm2'''/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 it will always start automatically when the machine boots.# Use the '''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 vm3) ==to allow IMAP connections from your local network and try '''nc''' again. Once it works, do not forget 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 set '''disable_plaintext_auth''' to '''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 changes take effect.

We are far from having a working email server but at this point we have enough === Connecting to be able to test it with IMAP Servers Using Thunderbird.===

The process is a little challenging because Thunderbird tries really hard to prevent you from connecting '''Perform the following steps:''' #On your '''host''' machine, return 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 '''vm2''' for '''SMTP ''' and '''vm3''' for '''IMAP'''. 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:

Thunderbird won't let you proceed with the <ol><li value="Done3" button because you will fail >Try to connect to your IMAPserver with Thunderbird by clicking on your '''Inbox'''.</li><li>If nothing happens, then check the Thunderbird Activity Manager for any errors. If the connection is successful, you should see the '''Trash''' box <u>appear</u> below Inbox. </li><li>Use the "Advanced config" button Thunderbird application to send an email to bypass your myseneca address. If you've done everything right, it will send the message successfully</li><li>Verify that checkyour 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:'''

Now use Thunderbird #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 an email to your myseneca any regular user <u>on</u> '''vm3''' using the email address'''yourusername@yoursenecaid. If youops'''ve done everything right - it will send using the message successfully but it will fail Thunderbird application on your host machine (which is configured to save it in use the Sent folder, because that's done with IMAP and you don't have an IMAP server yetaccount on your vm2).<br><br>

Still <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- verify that your time "test" if the mail message has been sentreceived on your VM3 machine (from your VM2 machine). Check <br><br>'''Note:''' It is <u>'''important'''</u> that you '''<u>don't</u>''' create this same account name on your myseneca vm2 machine, since you want to easily identify the difference between the sending and receiving SMTP servers.<br /><br /></li></ol> <ol><li value="3">Use the new account in Thunderbird to send an email to '''firstname@yoursenecaid.ops''' and look at 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 vm2 how you 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 server|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'''

Students should be prepared with '''all required commands (system information) displayed in a terminal (or multiple terminals) prior to calling ===Online Submission===Follow the instructor instructions for signofflab 4b on blackboard.<!--===Andrew'''.s sections===

'''Arrange evidence (command output) for each You may choose to:* Submit screenshots of these items your work on your screenBlackboard, then ask your instructor in which case you don't need to come to the lab.* Or come to review them and sign off on the lab, show me your work, and talk to me about it. I want to hear what you's completion:''ve learned and answer any questions you have. You'll get the same grade regardless of how you choose to submit your work.

#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?