MAIL SERVER RESOURCES
Online References:
- [ OPS335 Mail Server Notes ] Course Note providing Concepts and Overview of mail server setup
- Postfix for Dummies Good Basic Guide to setup Postfix MTA
OVERVIEW & PREPARATION
This lab will show you how to set up a Postfix email server using a Fedora 20 installation.
- You will need at least two systems to do this lab. If for some reason you have not set up your virtual machines, do so before continuing.
INVESTIGATION 1: INSTALL & SETUP MAIL TRANSFER AGENT (MTA) USING POSTFIX
- Ensure all machines have been updated and that the clocks are set to the correct date and time.
- Due to the changes made in this lab3, you will now need your vm1 running (as the DNS server) in order for any of your virtual machines to be able to use the internet.
Confirm Network Connections
Perform the following steps:
- Make certain that you can connect to the Internet on your Host Machine via web-browser. 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 Firefox 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 (NOTE: you should not have to authenticate yourself on the guest machine).
Install and configure Postfix on a VM
We will now be installing the postfix application which will act as the Mail Transfer Agent (MTA) that will send and receive e-mail messages between servers (VMs as well as servers that are outside of our virtual network).
Perform the following steps:
- Switch to your VM2 machine.
- Check the status of the sendmail 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):
yum install postfix
- What is the purpose of installing the postfix application in terms of using e-mail? Record your answer in your lab logbook.
NOTE: We need to configure the postfix application (i.e. our MTA) to recognize our recently-created domain name that we setup in lab3. - Edit the Postfix configuration file: /etc/postfix/main.cf and edit this file to contain only the contents displayed below:
mydomain = <senecaID>.org
- Create the database file of mail aliases
postalias hash:/etc/aliases
- Start and enable Postfix:
systemctl start postfix.service systemctl enable postfix.service
- Check your /var/log/messages file to see that your postfix servers started without error.
- If there are any errors, correct them before continuing.
- Check your /var/log/messages file to see that your postfix servers started without error.
Reviewing the mail command
Testing mail with the internet
- Test email from your machine by sending an email to your Seneca account.
mail -s "PART C3" <Your Seneca email address>
Note: <Your Seneca email address> is your Seneca email address.
Note: after you type in your letter, enter a period in the first column on the last line and hit the ENTER key.
- 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 the host by sending an email to your Seneca account.
mail -s "PART C4" -r hacker@evil.com <Your Seneca email address>
Note: after you type in your letter, enter a period in the first column on the last line and hit the ENTER key.
- 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 and Configure Postfix on a vm' on your VM 3.
Testing email using IP Addresses
- Adjust your firewall to allow traffic to port 25 on both VMs.
- Also check your /var/log/maillog file to see the log entries that get created when mail is sent and received, and when something goes wrong.
- Try sending an email from vm2 to your vm3.
mail -s "PART E2" yyyyyy@[192.168.X.4]
Note: yyyyyy is your Seneca ID
Note: the square brackets around the host IP address
- Try sending an email from your vm3 to vm2.
mail -s "PART E3" root@[192.168.X.3]
Test email using host names
- Use the host and hostname commands to check that each of your machines has the same hostname that the DNS service says they have.
- Restart postfix if you change the hostname on either mail server.
Now try sending mail to yourself on both machines. For example, as <senecaID> on VM 3, use the command:
$ mail <senecaID>@vm2.<yourdomain>.org
the machine will prompt for a subject: enter "testing" without the quotes.
- Now enter the body of your letter. When you're done, enter a period (.) in column 1 on the last line of your letter. This will signal end-of-file and your letter will be mailed. You should end up back at the $ prompt. If you mess up use CTRL-C to cancel the email, DO NOT USE CTRL-Z.
- Use the mailq command on both machines (you will need to be root) to view the mail queue.
Use the mail command to check if you have mail.
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 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 answers.