How to Configure a Basic Mail Server on Debian

Setting up a mail server may sound hard at first. I used to feel that way too. But once I broke it into small steps, it made a lot more sense.

In this guide, I’ll show you how to set up a simple mail server on Debian. It won’t be a fancy system with all the extras, but it will be good enough to send and receive email from your own domain.

I’ll walk you through each step and explain what’s going on. If you’re running a small website or just want to learn, this is a good place to start.

What Is a Mail Server?

A mail server is a program or machine that sends, receives, and stores email. When someone sends you an email, their server talks to your mail server to deliver it.

There are two main parts:

• SMTP (Simple Mail Transfer Protocol) – sends messages.
• IMAP or POP3 – lets you read messages.

For this setup, we’ll use Postfix for sending and Dovecot for reading.

What You’ll Need

Before you begin, make sure you have the following:

• A Debian server (Debian 10, 11, or newer is fine)
• A domain name (like yoursite.com)
• Root or sudo access
• Some time and patience

Do you have your domain ready? You’ll need to create DNS records for mail to work. I’ll help you with that later in the guide.

Step 1: Update Your Server

Start by updating your system.

sudo apt update
sudo apt upgrade -y

This keeps your system safe and makes sure you’re using the latest packages.

Step 2: Set the Hostname

Your server should have a proper name. Let’s set it to something like mail.yoursite.com.

sudo hostnamectl set-hostname mail.yoursite.com

Now edit the /etc/hosts file:

sudo nano /etc/hosts

Add a line like this (replace the IP and domain with yours):

127.0.1.1   mail.yoursite.com mail

Save and close the file.

Check if it worked:

hostname

It should now show mail.yoursite.com.

Step 3: Install Postfix (SMTP)

Postfix will let your server send email.

Install it:

sudo apt install postfix -y

During setup, you’ll see a few prompts:

• General type of mail configuration: Choose “Internet Site”.
• System mail name: Type your domain (like yoursite.com).

That’s it. Postfix is now installed.

Want to test it? Try:

echo "Test email body" | mail -s "Test Subject" [email protected]

Did it work? Check your email inbox (and spam folder).

Step 4: Install Dovecot (IMAP/POP3)

Dovecot will let you read emails with a mail client like Thunderbird or Outlook.

Install Dovecot:

sudo apt install dovecot-imapd dovecot-pop3d -y

By default, Dovecot will create a mailbox for each system user. That means if you add a new user, they can get email at [email protected].

You can test Dovecot with:

telnet localhost 143

If you see a greeting, it’s working.

Step 5: Create a Mail User

Let’s create a test user:

sudo adduser testuser

Set a password when asked.

This user can now receive email at [email protected].

Step 6: Configure DNS Records

Now it’s time to tell the world where to find your mail server.

Log in to your domain provider (like Namecheap, GoDaddy, or Cloudflare) and add:

1. MX Record

• Type: MX
• Host: @
• Value: mail.yoursite.com
• Priority: 10

2. A Record

• Type: A
• Host: mail
• Value: [your server’s IP address]

Wait a few minutes for the DNS to update.

To check if it’s working:

dig MX yoursite.com +short

You should see mail.yoursite.com.

Step 7: Test Email Sending and Receiving

Try sending a test email again:

echo "Hello again" | mail -s "Test 2" [email protected]

Now use a mail client (like Thunderbird) to check if you can log in and read mail from [email protected].

Use IMAP settings like:

• Incoming: mail.yoursite.com
• Port: 143 (or 993 for secure IMAP)
• User: testuser
• Password: your password

Step 8: Add SSL (Optional but Recommended)

Without SSL, your passwords and messages are sent in plain text. That’s risky.

You can use Let’s Encrypt to add SSL:

Install Certbot:

sudo apt install certbot -y

Then run:

sudo certbot certonly --standalone -d mail.yoursite.com

Now edit Dovecot and Postfix to use the new certificates.

For Postfix, edit /etc/postfix/main.cf:

smtpd_tls_cert_file=/etc/letsencrypt/live/mail.yoursite.com/fullchain.pem  
smtpd_tls_key_file=/etc/letsencrypt/live/mail.yoursite.com/privkey.pem  
smtpd_use_tls=yes

For Dovecot, edit /etc/dovecot/conf.d/10-ssl.conf:

ssl = yes  
ssl_cert = </etc/letsencrypt/live/mail.yoursite.com/fullchain.pem  
ssl_key = </etc/letsencrypt/live/mail.yoursite.com/privkey.pem

Restart both:

sudo systemctl restart postfix  
sudo systemctl restart dovecot

Your mail server is now more secure.

Two Helpful Lists

Mail Server Tools Used in This Guide:

• Postfix – handles outgoing mail (SMTP)
• Dovecot – lets users read mail (IMAP/POP3)
• Certbot – adds free SSL to your server
• Dig / Telnet – for testing DNS and ports

Benefits of Hosting Your Own Mail Server:

• You control your data
• No monthly fees
• Good for testing, learning, or small sites
• Works with your own domain

Self-Hosting vs Gmail (Comparison)

If you’re just learning or hosting mail for a few users, your own server is a good option. But if you want no setup at all and strong spam filters, Gmail is hard to beat.

Final Thoughts

Running your own mail server is a great learning experience. It helps you understand how email works behind the scenes.

Here’s a quick recap:

• You installed Postfix and Dovecot
• You created a user and DNS records
• You tested sending and receiving
• You added SSL for security

This is just a basic setup. There’s more you can add later, like spam filters, webmail, or DKIM/DMARC for better email delivery.

Have you ever thought about self-hosting your email before? What would you use it for?