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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.

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Path Info

Level
Clock icon Intermediate
Duration
Clock icon 45m
Published
Clock icon Sep 26, 2022

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Table of Contents

  1. Challenge

    Log In to the Provided Server

    Log in to the server as cloud_user with the provided password. When the SERVER-READY file is shown in the /home/cloud_user folder, you can then follow along with the tasks.

  2. Challenge

    Install the Postgrey Greylisting Software

    Using the dnf or yum system commands, install the postgrey package. Start the software and set it to auto-start on system reboot.

  3. 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.

  4. 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 the testuser and checking email.

    su - testuser

mailx

    This should show you your email.

A Cloud Guru - Labs - Postfix with Greylisting
Author
A Cloud Guru

The Cloud Content team comprises subject matter experts hyper focused on services offered by the leading cloud vendors (AWS, GCP, and Azure), as well as cloud-related technologies such as Linux and DevOps. The team is thrilled to share their knowledge to help you build modern tech solutions from the ground up, secure and optimize your environments, and so much more!

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