Prerequiste

I assume that you have a Centos installation.

SMTP

You can copy/paste this script and use it to configure automatically your server.

#!/bin/bash
 
echo "install postfix"
dnf -y install postfix
dnf -y remove sendmail # make postfix the default MTA
 
echo "start service"
systemctl start postfix.service
 
echo "configure postfix"
 
# comments all:
sed -i "s/^\(inet_interfaces = \)/#\1/" /etc/postfix/main.cf
sed -i "s/^\(mydestination = \)/#\1/" /etc/postfix/main.cf
 
# remove comments:
sed -i "s/^#\(inet_interfaces = all\)/\1/" /etc/postfix/main.cf
sed -i "s/^#\(home_mailbox = Maildir\/\)/\1/" /etc/postfix/main.cf
sed -i "s/^#\(mydestination = \$myhostname, localhost.\$mydomain, localhost, \$mydomain\)$/\1/" /etc/postfix/main.cf
 
echo "reload postfix"
systemctl reload postfix.service
 
echo "add service smtp (port 25) to firewall"
firewall-cmd --permanent --add-service smtp
firewall-cmd --reload
 

Testing email

Inside the server

First, we create our email file ’email.txt’:

Subject: my subject
my message

Then, send it:

sendmail -v example@gmail.com < email.txt

Outside the server

$> telnet srv-mail 25
$> 
helo srv-mail
mail from:<noreply@gmail.com>
rcpt to:<my-email@gmail.com>
data
From: noreply@gmail.com
Subject: test mail from command line
 
this is my tiny message
sent from linux
.

IMAP / POP

You can copy/paste this script and use it to configure automatically your server.

#!/bin/bash
 
echo "install dovecot"
dnf -y install dovecot
 
echo "configure dovecot"
sed -i "s/^#\(protocols\s*=\)/\1/" /etc/dovecot/dovecot.conf
 
echo "start service dovecot on boot"
systemctl enable dovecot.service
 
echo "start service"
systemctl start dovecot.service
 
 
echo "open pop3 port (i.e 110) and imap (i.e. 143)"
firewall-cmd --permanent --add-service dovecot