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Linux CentOS 7 - Postfix configuration

Linux CentOS 7 - Postfix configuration


Configure system1 as a mail server and system2 as a null client.
From the null client, user alice can send mails to user bob on the mail server.

On system1 and system2

Install the packages:
# yum install -y postfix mailx

Enable and start the service:
# systemctl start postfix
# systemctl enable postfix

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


On system1

Configure the server

vim /etc/postfix/main.cf
myhostname = system1.example.com
mydomain = example.com
myorigin = $mydomain
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
inet_interface = all
mynetworks = 192.168.189.0/24, 127.0.0.0/8
inet_protocols = ipv4

Check the configuration
postfix check

Restart the service
systemctl restart postfix

Add user bob
useradd bob

Check bob received alice's message

su - bob
mail
type 1

From alice@example.com  Sun Jun 23 21:57:45 2019
Return-Path: <alice@example.com>
X-Original-To: bob@example.com
Delivered-To: bob@example.com
Date: Sun, 23 Jun 2019 21:57:45 +0200
To: bob@example.com
Subject: test
User-Agent: Heirloom mailx 12.5 7/5/10
Content-Type: text/plain; charset=us-ascii
From: alice@example.com
Status: R

hi bob, how are you?

& exit



On system2

Configure the null client
vim /etc/postfix/main.cf
myhostname = system2.example.com
mydomain = example.com
myorigin = $mydomain
mydestination =
inet_interface = loopback-only
relayhost = 192.168.189.143
mynetworks = 127.0.0.0/8 
inet_protocols = ipv4 
local_transport = error: local delivery disabled 


Check the configuration
postfix check

Restart the service
systemctl restart postfix

Add user alice
useradd alice

As user alice,  send an email to bob
su - alice
mail -s test bob@example.com
hi bob, how are you?
.
exit

Check the post queue
postqueue -p

Flush the post queue
postqueue  -f

Check the mail log in real time
tail -f /var/log/messages



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