This is a tutorial how to install your own mail server on a Rocky Linux 9 machine.
Update system.
dnf update -y
Set your timezone.
timedatectl set-timezone UTC
date
Set the machine hostname.
hostnamectl set-hostname my.domain
dnf install epel-release
dnf update
Install nano text editor, a nice monitor, and terminal multiplexer.
dnf install nano htop tmux
Reboot system, login back to server (as root).
reboot
dnf -y install postfix
Edit the server configuration file nano /etc/postfix/main.cf and change the following:
# uncomment and specify hostname
myhostname = mail.srv.world
# uncomment and specify domain name
mydomain = srv.world
# uncomment
myorigin = $mydomain
# listen on all network interfaces
inet_interfaces = all
# change it for ipv4 only
inet_protocols = ipv4
# uncomment and add more domains
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
# uncomment and specify your local network
mynetworks = 127.0.0.0/8, 10.0.0.0/24
# or, set to only trust local host
mynetworks_style = host
# uncomment home mailbox location (use Maildir)
home_mailbox = Maildir/
# uncomment this line (without version)
smtpd_banner = $myhostname ESMTP $mail_name
# add next setting in the end of the file
# disable SMTP VRFY command
disable_vrfy_command = yes
# require HELO command to sender hosts
smtpd_helo_required = yes
# limit an email size
# example below means 10M bytes limit
message_size_limit = 10240000
# SMTP-Auth settings
smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth
smtpd_sasl_auth_enable = yes
smtpd_sasl_security_options = noanonymous
smtpd_sasl_local_domain = $myhostname
smtpd_recipient_restrictions = permit_mynetworks, permit_auth_destination, permit_sasl_authenticated, reject
Enable and start postfix server.
systemctl enable --now postfix
Check postfix server status.
Edit the postfix configuarion file:
nano /etc/postfix/main.cf
Consider carfually before adding the following settings, they might reject messages that you do not intened.
Add the following settings:
# reject unknown clients that forward lookup and reverse lookup of their hostnames on DNS do not match
smtpd_client_restrictions = permit_mynetworks, reject_unknown_client_hostname, permit
# rejects senders that domain name set in FROM are not registered in DNS or
# not registered with FQDN
smtpd_sender_restrictions = permit_mynetworks, reject_unknown_sender_domain,reject_non_fqdn_sender
# reject hosts that domain name set in FROM are not registered in DNS or
# not registered with FQDN when your SMTP server receives HELO command
smtpd_helo_restrictions = permit_mynetworks, reject_unknown_hostname,reject_non_fqdn_hostname, reject_invalid_hostname, permit
Restart postfix server:
systemctl restart postfix
Install firewalld:
dnf install -y firewalld
Run firewall service:
systemctl start firewalld.service
Add SMTP (port 25) to firewall:
firewall-cmd --add-service=smtp
firewall-cmd --runtime-to-permanent
Check firewall status:
firewall-cmd --list-all