Install Postfix

Set hostname (REQUIRED)

Postfix is very sensitive to the system hostname.

hostnamectl set-hostname mail.yourdomain.id

Edit /etc/hosts:

nano /etc/hosts

Add:

127.0.1.1   mail.yourdomain.id mail

Verify:

hostname
hostname -f

The output must be:

mail.yourdomain.id

apt update
apt install postfix mailutils -y

When the setup wizard appears, choose:

General type: Internet Site
System mail name: mail.yourdomain.id

Check Postfix service

systemctl status postfix
ss -lntp | grep :25

Postfix must be listening on port 25.

Basic Postfix hardening

Edit the configuration file:

nano /etc/postfix/main.cf

Ensure the following settings:

myhostname = mail.yourdomain.id
mydomain = yourdomain.id
myorigin = $mydomain

inet_interfaces = all
inet_protocols = ipv4

mydestination = $myhostname, localhost.$mydomain, localhost
mynetworks = 127.0.0.0/8, [::1]

home_mailbox = Maildir/

smtpd_banner = $myhostname ESMTP

# Prevent open relay
smtpd_recipient_restrictions =
    permit_mynetworks,
    permit_sasl_authenticated,
    reject_unauth_destination

Restart Postfix:

systemctl restart postfix

Test local email delivery

echo "Postfix OK" | mail -s "Test Email" root

Check inbox:

mail

Test outbound (internet) email

echo "Hello from Ubuntu Postfix" | mail -s "Test SMTP" your@gmail.com

Monitor the mail log:

tail -f /var/log/mail.log

–have trying..

Install Postfix – Ubuntu 24.04