Postfix with Greylisting

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.

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

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.

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.