How to Install SMTP Server in Ubuntu 25.04

Setting up an SMTP server on Ubuntu 25.04 lets your system send emails — for alerts, password resets, cron jobs, and more. The most common and reliable way is using Postfix, a widely used Mail Transfer Agent (MTA).

Step 1: Update system packages

Before installing any new software, it’s a good idea to update your current packages to avoid dependency problems:

sudo apt update && sudo apt upgrade -y

This ensures your system is ready for a smooth Postfix installation.

Step 2: Install Postfix

Postfix is a lightweight and fast SMTP server. Installing it is simple with Ubuntu’s package manager:

sudo apt install postfix -y

When prompted, select Internet Site and enter your server’s domain name (like mail.example.com).

Step 3: Reconfigure Postfix (optional)

If you entered the wrong domain or want to change settings, you can reconfigure Postfix anytime using this command:

sudo dpkg-reconfigure postfix

It lets you modify hostname, mail type, and delivery settings interactively.

Step 4: Open SMTP ports

If you’re using UFW (Uncomplicated Firewall), you need to allow SMTP traffic on standard ports like 25 and 587:

sudo ufw allow 25
sudo ufw allow 587

Then reload the firewall rules:

sudo ufw reload

Step 5: Check Postfix status

To confirm that the SMTP service is running properly, check the Postfix system status:

sudo systemctl status postfix

You should see active (running). If not, restart the service:

sudo systemctl restart postfix