General Information

Configuring postfix.

On the exam, you will be provided all the information of an already configured central SMTP server.

You will be expected to configure a null client only. (server that forwards mail but does not receive any)

THIS IS ON THE EXAM: A mail null client forwards local email. It does not receive any mail from network sources.

From server1.

Install required package

yum install postfix

Enable and start the postfix service

systemctl enable postfix
systemctl start postfix

Edit the main configuration

vim /etc/postfix/main.cf
 
## Set the origin (where mail came from) to the domain variable
myorigin = $mydomain
 
# Relayhost to forward mail to
relayhost = [192.168.1.151]
 
# Forward from loopback interfaces and networks only (local system)
inet_interfaces = loopback-only
mynetworks = 127.0.0.0/8 [::1]/128
 
# Configure destination as blank, because we aren't delivering mail locally (only forwarding outgoing)
mydestination = 
 
# Prevent postfix from putting mail into mail boxes
local_transport = error: local delivery disabled

Check postfix syntax

postfix check

Restart the service

systemctl restart postfix

THIS IS NOT ON THE EXAM: This section setups up a mail server to receive mail in order to test the null client configured previously.

From server2

Install postfix

yum install postfix

Enable and start postfix

systemctl enable postfix
systemctl start postfix

Open the firewall to receive SMTP

firewall-cmd --permanent --add-service=smtp
firewall-cmd --reload

Edit the main configuration file

vim /etc/postfix/main.cf
 
inet_interfaces = all
inet_protocols = ipv4
mydestination = example.com, server2.example.com, server2

Restart the service

systemctl restart postfix

From server1.

Install a mail client (if not already installed)

yum install mailx

Send a test message

echo "This is the subject body" | mail -s "This is a postfix forward test" root@server2.example.com

Watch the mail log file for status messages

tail -f /var/log/maillog