- Lab
-
Libraries: If you want this lab, consider one of these libraries.
- Cloud

Postfix with Greylisting
In this lab, you will be provided with a Linux CentOS server that has Postfix and greylisting installed but not configured. Your task is to configure the software so that incoming emails are sent through the greylisting process. The purpose of this lab is to have you configure Postfix to use the greylisting policy. Once configured, you will verify that Postfix is directing incoming email through the greylisting process.

Lab Info
Table of Contents
-
Challenge
Log In to the Provided Server
Log in to the server as
cloud_user
with the provided password.When theSERVER-READY
file is shown in the/home/cloud_user
folder, you can then follow along with the tasks. -
Challenge
Install the Postgrey Greylisting Software
Using the
dnf
oryum
system commands, install thepostgrey
package. Start the software and set it to auto-start on system reboot. -
Challenge
Configure the Postfix Configuration File to Use the Postgrey Service
Edit the
/etc/postfix/main.cf
file and add the Postgrey policy service so incoming emails get greylisted on arrival.Restart the Postfix email server.
-
Challenge
Test That Postgrey Is Intercepting Emails
Test that the Postfix service is using Postgrey to intercept emails.
When testing, you should see a Recipient address rejected message.
When you retry after 60 seconds, the email should now be accepted.
An example of using the
telnet
program to connect to a local email system is as follows:telnet localhost 25 ehlo localhost mail from: cloud_user rcpt to: testuser
At this time, you should see a message saying you have been greylisted for 60 seconds.
Wait 60 seconds and try the command again:
rcpt to: testuser
This should allow you to continue with the task of sending email data.
Now you can test by using the
su
command to sudo to thetestuser
and checking email.su - testuser mailx
This should show you your email.
About the author
Real skill practice before real-world application
Hands-on Labs are real environments created by industry experts to help you learn. These environments help you gain knowledge and experience, practice without compromising your system, test without risk, destroy without fear, and let you learn from your mistakes. Hands-on Labs: practice your skills before delivering in the real world.
Learn by doing
Engage hands-on with the tools and technologies you’re learning. You pick the skill, we provide the credentials and environment.
Follow your guide
All labs have detailed instructions and objectives, guiding you through the learning process and ensuring you understand every step.
Turn time into mastery
On average, you retain 75% more of your learning if you take time to practice. Hands-on labs set you up for success to make those skills stick.