The following guide assumes you have basic knowledge about Linux administration, including being comfortable with the command-line interface (CLI). Follow the steps below to set up a mail server with Postfix on a Virtual Private Server (VPS).
This guide will walk you through setting up Postfix as the SMTP server, but you’ll need additional software to handle POP/IMAP and webmail.
Step 1: Update Your System.
Before starting any software installation, it’s always a good idea to update your system packages to avoid any software dependencies later on. Use the following command to update all the packages:
```
sudo apt-get update
sudo apt-get upgrade
```
Step 2: Install Postfix.
In this step, you will install Postfix using the command below:
```
sudo apt-get install postfix
```
During the installation process, an installation wizard will guide you. You will be asked some questions regarding your new mail server. Here’s how to answer:
- General type of mailing configuration: Internet Site
- System mail name: your domain name (like ‘server.com’)
Step 3: Configuring Postfix.
The main configuration file for Postfix is /etc/postfix/main.cf. The following command will open the file in a text editor:
```
sudo nano /etc/postfix/main.cf
```
In this file, you’ll need to set up several parameters:
```
myhostname = mail.your-domain.com
mydomain = your-domain.com
myorigin = $mydomain
inet_interfaces = all
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
mynetworks = 127.0.0.0/8, your_network/24
home_mailbox = Maildir/
```
After making all the changes, save the changes and exit the editor.
Now you need to reload the Postfix daemon to make these changes come into effect:
```
sudo systemctl reload postfix
```
Step 4: Configuring the Firewall.
In case you have a firewall, you will have to open the SMTP and Submission ports:
```
sudo ufw allow Postfix
```
Step 5: Testing the SMTP Server.
In this step, you will check whether the SMTP server is working correctly:
```
telnet localhost 25
```
After you’re done, type:
```
quit
```
You have now installed and configured your Postfix mail server. Please keep in mind that this is a basic setup and actual production server may require additional steps such as setting up an IMAP/POP3 server (Dovecot is commonly used), implementing SSL for mail security, etc.
Also note that if you are hosting on a VPS from Amazon, Google or Azure there might be additional steps or restrictions for sending mail directly from your server to prevent spam. It might be necessary to use a 3rd party relay service like SendGrid or SES.
