Install the software 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).

SSH as root with password login?

By default the server will not allow logging in as “root” over SSH for security reasons. Instead use the non-root user you created during the installation. Then enter “su -” to become root. I recommend you use SSH public key authentication which means creating an SSH key (if you don’t have one yet) using ssh-keygen on your workstation and and ssh-copy-id to copy your public key file from ~/.ssh/id_rsa.pub file to ~/.ssh/authorized_keys on the server. If logging in still does not work please check the /var/log/auth.log file on the server. You may have some permissions wrong.

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

apt update
apt upgrade


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 MySQL server that will store information about your email accounts and domains. In previous versions this package was called “mysql-server”. MySQL was bought by SUN Microsystems which was later bought again by Oracle. Its original developer Monty was not happy with Oracle and thus maintained the software under the new name MariaDB. (Maria and My are the names of Monty’s children.) So basically MariaDB is a fork of MySQL. Both pieces of software started to evolve in slightly different directions. However Linux distributions decided to go with the most open-sourcy way thus choosing MariaDB. So basically MariaDB is what you knew as MySQL. The “other” MySQL is available directly from Oracle. I just wonder how much I trust a commercial database maker with sponsoring a competing open-source product.
  • postfix
    The MTA (mail transport agent) that speaks SMTP and receives and sends emails.
  • postfix-mysql
    An extension that allows Postfix to get its information from a MySQL database. (Yes, it’s compatible with MariaDB.)
  • dovecot-mysql
    The IMAP/POP3 mail server including an extension to query information from a MariaDB database.
  • dovecot-pop3d
    An extension to Dovecot that allows users to fetch emails using the POP3 protocol. (This is optional. Only few users nowadays 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 to make Postfix send emails to Dovecot for storage.
  • dovecot-managesieved
    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 php7.0
    The web server that powers the webmail interface. PHP is the scripting language that the Roundcube webmail software is written in.
  • adminer
    A web interface to manage your SQL database.
  • 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 create and renew certificates.
  • 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
    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.


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.


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 php7.4


I have been asked several times why endorse Apache. Why not use Nginx instead? Well, Apache is still pretty common. And if you use PHP – which we need for the web mail software – there is no performance advantage of using Nginx anyway. If you prefer Nginx then go with it – PHP will run fine there with PHP-FPM.


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

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


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

apt install -y swaks


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


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


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


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


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

3 thoughts on “Install the software packages

  • 2021-11-25 at 13:54

    Hi Christoph,

    Thanks again for the (every time even better) ISPmail guide. I have a question, reading the selected packages: Why PHP7 and not PHP8? Since support for PHP8 most likely will be longer…


    • 2021-11-25 at 14:21

      Hi Richard. I wasn’t aware there is PHP8 in Debian Bullseye. Are you sure?

      • 2021-11-25 at 14:45

        Hi christoph, you’re right, it isn’t (yet). mixed up debian/ubuntu/manual actions.


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