How to Install SMTP Server on Ubuntu?

You need a mail server, whether you're an individual, a small business, or an enterprise. This system allows you to collect, send, and process email messages. Having control over your own mail server comes with several benefits, such as customization, scalability, and security.

One such popular option is SMTP (Simple Mail Transfer Protocol). This email server is designed to receive and relay emails between the sender and receiver. Without a server, you are only limited to sending and receiving emails from a similar domain; however, an SMTP email server is more comprehensive and allows you to establish an internet communication protocol with different addresses.

How do you install an SMTP server on Ubuntu? This guide will provide step-by-step instructions to enable you to send and receive emails securely within your own environment.

How Does An SMTP Server Work?

The SMTP networking protocol works by allowing data interchange between different servers or PCs. It works on all systems, no matter the hardware or software in place. The biggest advantage of this protocol is the standardized email transmission that makes it easy to relay emails over any network. 

Like mail delivery from the postal service, SMTP routes the outgoing email to the email provider’s server. Once the emails have been retrieved, the recipient can view them. Additionally, the SMTP protocol informs the sender if the email can’t be delivered. 

To install SMTP on Ubuntu, you can use the popular mail server software, Postfix. This mail transfer agent (MTA) comes in handy when you need to send a large volume of emails or when a third-party email service provider doesn’t allow you to relay email notifications from your business apps. It has extensive features that help you maintain your SMTP server. 

•  When an email is sent from an application or client email, it connects to your SMTP server.
• The sender’s SMTP client initiates a connection with the mail transfer agent. At this stage, the server may request for the sender’s identity or authentication. 
• The sender’s clients offers the recipient’s email content, address, and other attachments. 
• The SMTP server conducts checks to confirm that the recipient’s email address exists, and once the check passes, the server relays the email message to the recipient's SMTP server.
• The recipient's SMTP server receives the email and stores it for the recipient.
• The recipient's application retrieves the email from the mailbox using different protocols. 
• In some cases, the email can be forwarded to another server until it gets to the final recipient. 

Prerequisites

You need:

• System operating on Ubuntu
• A non-root user

Step-by-Step Guide to Instal SMTP Server on Ubuntu

Step 1: Update the Server

Before starting any installation process, you must log in and update your server. Once you confirm that your server is using the latest Ubuntu package lists, run this command:

sudo apt update

Step 2: Install Postfix

Next, you need to install Postfix by running this command:

sudo apt install postfix

During the installation process, a pop-up configuration window will appear. You’ll get prompted to select the type of mail configuration. Pick “Internet Site” and press the Enter tab. After the installation process is complete, you can move to configuration.

Step 3: Configure Postfix

To receive and send emails, you need to have Postfix configured. To achieve this, you can set up Postfix to be the exclusive system in the interface. This interface is an important virtual network that helps servers communicate internally. 

To add the modifications, you’ll need to open the main configuration file (main. cf) for Postfix using a text editor. However, remember to back up your files before making any changes. To access these files, input this command:

sudo nano /etc /postfix/ main.cf

Once you find the files, pay attention to inet_interfaces and set the value to loopback-only.

mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = loopback-only

Once done, save the configuration file to keep all the changes. You can effect these changes by opening the Postfix server.

Step 4: Test the Server

After configuration, you must ensure the SMTP server is working properly on Ubuntu email servers. Telnet can help you conduct this test. 

You can check if the local host is connected by installing the mail-sending packages of Postfix. Use this command:

sudo apt install bsd-mailx

Once the installation is done, replace the details with your actual email address and conduct a real test.

Step 5: Configure Firewall

On most occasions, the firewall may limit Postfix. However, you can remove these restrictions using these commands: 

sudo ufw allow “Postfix”

sudo ufw “Postfix SMTPS”

sudo ufw allow “Postfix Submission”

With this configuration in place, your Postfix is now ready for use.

Summary

Setting up an SMTP server on Ubuntu using Postfix provides you with a reliable and customizable solution for managing your email communication. This step-by-step installation and configuration process will help you install this server without any errors. Hosting your SMTP server on Ubuntu allows you to easily send and receive emails, especially if you handle bulk email messages for your startup or large enterprise.