Install packages

After the basic installation your server will reboot and allow you to login. You can either login at the console (if you have physical access to the system) or using SSH (secure shell).

Unless you just installed the server it is a good idea to install all missing updates first:

apt update
apt upgrade

Packages

Let us install the necessary Debian packages to make it an actual mail server. Take a moment to read through this list of package – we will do the installation afterwards:

• mariadb-server
  The database service that will store information about your email accounts and domains. (If you haven’t heard of MariaDB yet, it is a fork of MySQL after being acquired by Oracle.)
• postfix
  The MTA (mail transport agent) that speaks SMTP to receive and send emails.
• postfix-mysql
  An extension that allows Postfix to get its information from a MySQL/MariaDB database.
• dovecot-mysql
  The IMAP/POP3 mail server including an extension to query information from a MySQL/MariaDB database.
• dovecot-pop3d (optional)
  An extension to Dovecot that allows users to fetch emails using the POP3 protocol. (This is optional. Only few users nowadays still use POP3.)
• dovecot-imapd
  An extension to Dovecot that allows users to access emails using the IMAP protocol.
• dovecot-lmtpd
  Enables Dovecot to receive LMTP connections. We will need it later for the internal transfer of emails from Postfix to Dovecot.
• dovecot-managesieved (optional)
  An extension to Dovecot that allows users to define filter rules that are automatically run on the server when a new email arrives.
• apache2 and php8.2
  The web server that powers the webmail interface. PHP is the scripting language that the Roundcube webmail software is written in.
• adminer (optional)
  A web interface to manage your SQL database if you are not comfortable crafting SQL queries by hand.
• rspamd
  A third-party software that deals with spam and handles automatic domain key (DKIM) signing.
• redis-server
  A key-value store. It is a simple but fast kind of database service where Rspamd stores training data about spam and ham.
• pwgen
  A tool to create random passwords.
• swaks
  The SWiss Army Knife of Smtp. A utility to send emails through SMTP for testing purposes.
• mutt
  A console-based program that can speak IMAP and also read Maildirs directly. Very helpful for testing the functionality of your mail server.
• certbot
  A tool that talks to the LetsEncrypt certificate service to request and renew certificates. You will not need it if you have bought a certificate for your webmail server.
• ca-certificates
  A set of certificates from common certificate authorities on the internet. It is required for the proper function of wget for example.
• fail2ban (optional)
  A daemon that tracks log files to recognize brute force attacks. It can block IP addresses of attackers. We will use it to defend against evil people trying to get into our mail server.

pwgen

Let’s start with the pwgen utility. It helps you create secure passwords. Unless you already have a tool for that…

apt install -y pwgen

You will need a random passwords later to create a database user for the mail server. Just as an example: to create a secure password having a length of 20 characters you would run:

pwgen -s 20 1

That gets you a string like “W2EzNUFJzjEmA8tQT7A0”.

MariaDB server

If you used MySQL before you may remember that you were forced to specify a password for the ‘root’ database user. That has changed with MariaDB in Debian – for the better. Now you can access the database server without any password if you are logged in as ‘root’ on the server. You might as well set a password but it is not necessary.

Go install the MariaDB server package:

apt install -y mariadb-server

If all went well you can now run “mysql” and get a connection to your MySQL database:

root@buster:~# mysql
 Welcome to the MariaDB monitor.  Commands end with ; or \g.
 Your MariaDB connection id is 30
 Server version: 10.3.18-MariaDB-0+deb10u1 Debian 10
 Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
 Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
 MariaDB [(none)]> 

Exit the SQL shell by typing “exit” or pressing CTRL-D.

Postfix

Now on to the Postfix packages:

apt install -y postfix postfix-mysql

When you get asked for the mail server configuration type please choose “Internet site”. Enter your own mail server name (the fully qualified domain name) or just press enter. The host name and domain does not need to match any of your email domains.

Apache and PHP

To provide a webmail service you need the Apache web server software and the PHP scripting language support:

apt install -y apache2 php8.2

rspamd

Just like in previous versions of this guide we will deal with spam using rspamd. (The rspamd principal developer endorses his own software packages but in this guide we will use the packages in Debian for stability.)

We also install Redis as a storage backend for Rspamd to store its training data about spam and ham.

apt install -y rspamd redis-server

swaks

A very useful tool to test email delivery later is SWAKS (the SWiss Army Knife for Smtp):

apt install -y swaks

mutt

This is a full-featured IMAP mail client. Think of it as the vi of mail clients. It cannot display HTML but it is very helpful to test IMAP mail servers. And some hardcore users still prefer it over any other mail client.

apt install -y mutt

certbot

You will want to use encrypted connections where possible. So you need a certificate for your services. The certbot software helps you to request and manage Let’s Encrypt certificates automatically.

apt install -y certbot

Dovecot

In addition to Postfix (that handles SMTP communication) you will need Dovecot to store received emails and provide IMAP (and optionally POP3) access for your users:

apt install -y dovecot-mysql dovecot-pop3d dovecot-imapd dovecot-managesieved dovecot-lmtpd

Adminer

SQL databases are called like that because SQL (structured query language) is the way you talk to it. But as we are just puny humans let’s have a more user-friendly way to manage the database. I suggest Adminer which is a tool similar to phpMyAdmin.

apt install -y adminer

ca-certificates

To avoid errors when downloading files using wget you should install the default set of certificates of common certificate authorities on the internet:

apt install -y ca-certificates