ISPConfig Perfect Multiserver setup on Ubuntu 20.04 and Debian 10 - Page 4

5 Installing the second mailserver

Log in as root or run

su -

to become root user on your server before you proceed. IMPORTANT: You must use 'su -' and not just 'su', otherwise your PATH variable is set wrong by Debian.

5.1 Configure the hostname

The hostname of your server should be a subdomain like "". Do not use a domain name without a subdomain part like "" as hostname as this will cause problems later with your mail setup. First, you should check the hostname in /etc/hosts and change it when necessary. The line should be: "IP Address - space - full hostname incl. domain - space - subdomain part". For our hostname, the file shall look like this:

nano /etc/hosts localhost.localdomain   localhost
# This line should be changed on every node to the correct servername: mx2
# These lines are the same on every node: panel web01 mx1 mx2 ns1 ns2 webmail # The following lines are desirable for IPv6 capable hosts ::1 localhost ip6-localhost ip6-loopback ff02::1 ip6-allnodes ff02::2 ip6-allrouters

As you can see, we added the hostnames of our other servers aswell, so they can communicate over the internal network later.

Then edit the /etc/hostname file:

nano /etc/hostname

It shall contain only the subdomain part, in our case:


Finally, reboot the server to apply the change:

systemctl reboot

Log in again and check if the hostname is correct now with these commands:

hostname -f

The output shall be like this:

[email protected]:~$ hostname
[email protected]:~$ hostname -f

5.2 Installing ISPConfig

Now we can run the autoinstaller for all packages and ISPConfig:

wget -O - | sh -s -- --no-dns --no-roundcube --no-mailman --use-php=system --use-unbound --interactive

After some time, you will see:

WARNING! This script will reconfigure your complete server!
It should be run on a freshly installed server and all current configuration that you have done will most likely be lost!
Type 'yes' if you really want to continue:

Answer "yes" and hit enter. The installer will now start.

When the installation and configuration of the packages is done, the root password for MySQL on mx2 will be shown. Write this down (along with the servername, to prevent any confusion later).

Now we will have to answer some questions as we are using interactive mode. This is necessary as this server will be added to your multiserver setup.

[INFO] Installing ISPConfig3.
[INFO] Your MySQL root password is: kl3994aMsfkkeE

 _____ ___________   _____              __ _         ____
|_   _/  ___| ___ \ /  __ \            / _(_)       /__  \
  | | \ `--.| |_/ / | /  \/ ___  _ __ | |_ _  __ _    _/ /
  | |  `--. \  __/  | |    / _ \| '_ \|  _| |/ _` |  |_ |
 _| |_/\__/ / |     | \__/\ (_) | | | | | | | (_| | ___\ \
 \___/\____/\_|      \____/\___/|_| |_|_| |_|\__, | \____/
                                              __/ |

>> Initial configuration  

Operating System: Debian 10.0 (Buster) or compatible

    Following will be a few questions for primary configuration so be careful.
    Default values are in [brackets] and can be accepted with <ENTER>.
    Tap in "quit" (without the quotes) to stop the installer.

Select language (en,de) [en]: <-- Hit enter

Installation mode (standard,expert) [standard]: <-- expert

Full qualified hostname (FQDN) of the server, eg server1.domain.tld  []: <-- Hit Enter

MySQL server hostname [localhost]: <-- Hit Enter

MySQL server port [3306]: <-- Hit Enter

MySQL root username [root]: <-- Hit Enter

MySQL root password []: <-- Enter the MySQL password the script just gave you

MySQL database to create [dbispconfig]: <-- Hit Enter

MySQL charset [utf8]: <-- Hit Enter

The next two questions are about the internal ISPConfig database user and password.
It is recommended to accept the defaults which are 'ispconfig' as username and a random password.
If you use a different password, use only numbers and chars for the password.

ISPConfig mysql database username [ispconfig]: <-- Hit Enter

ISPConfig mysql database password [aakl203920459853sak20284204]: <-- Hit Enter

Shall this server join an existing ISPConfig multiserver setup (y,n) [n]: <-- y

MySQL master server hostname []: <--

MySQL master server port []: <-- Hit Enter

MySQL master server root username [root]: <-- Hit Enter

MySQL master server root password []: <-- the password you gave the external root user on the master server.

MySQL master server database name [dbispconfig]: <-- Hit Enter

Adding ISPConfig server record to database.

Configure Mail (y,n) [y]: <-- Hit enter

Configuring Postgrey
Configuring Postfix
Generating a RSA private key
writing new private key to 'smtpd.key'
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
Country Name (2 letter code) [AU]: <-- Hit enter
State or Province Name (full name) [Some-State]: <-- Hit enter
Locality Name (eg, city) []: <-- Hit enter
Organization Name (eg, company) [Internet Widgits Pty Ltd]: <-- Hit enter
Organizational Unit Name (eg, section) []: <-- Hit enter
Common Name (e.g. server FQDN or YOUR name) []: <-- Hit enter
Email Address []: <-- Hit enter
[WARN] autodetect for Mailman failed
Force configure Mailman (y,n) [n]: <-- Hit enter

Skipping Mailman

Configuring Dovecot
Creating new DHParams file, this takes several minutes. Do not interrupt the script.
Configuring Spamassassin
[WARN] autodetect for Amavisd failed
Force configure Amavisd (y,n) [n]: <-- Hit enter

Skipping Amavisd

Configuring Rspamd
Configuring Getmail
Configuring Jailkit
Configuring Pureftpd
Configure DNS Server (y,n) [y]: <-- n

The Web Server option has to be enabled when you want run a web server or when this node shall host the ISPConfig interface.
Configure Web Server (y,n) [y]: <-- Hit enter

Configuring Apache
Configuring vlogger
[WARN] autodetect for OpenVZ failed
Force configure OpenVZ (y,n) [n]: <-- Hit Enter

Skipping OpenVZ

Configure Firewall Server (y,n) [y]: <-- Hit Enter

Configuring Ubuntu Firewall
[WARN] autodetect for Metronome XMPP Server failed
Force configure Metronome XMPP Server (y,n) [n]: <-- Hit Enter

Skipping Metronome XMPP Server

Configuring Fail2ban
Install ISPConfig Web Interface (y,n) [n]: <-- Hit Enter

Do you want to create SSL certs for your server? (y,n) [y]: <-- Hit Enter

Checking / creating certificate for
Using certificate path /etc/letsencrypt/live/
Using apache for certificate validation
Symlink ISPConfig SSL certs to Postfix? (y,n) [y]: <-- Hit Enter

Symlink ISPConfig SSL certs to Pure-FTPd? Creating dhparam file may take some time. (y,n) [y]: <-- Hit Enter

Generating DH parameters, 2048 bit long safe prime, generator 2
This is going to take a long time
Configuring Apps vhost
Configuring DBServer
Installing ISPConfig crontab
no crontab for getmail
Detect IP addresses
Restarting services ...
Installation completed.
[INFO] Adding php versions to ISPConfig.
[INFO] Checking all services are running.
[INFO] mysql: OK
[INFO] clamav-daemon: OK
[INFO] postfix: OK
[INFO] bind9: OK
[INFO] pureftpd: OK
[INFO] apache2: OK
[INFO] rspamd: OK
[INFO] redis-server: OK
[INFO] dovecot: OK
[INFO] Installation ready.
[INFO] Your MySQL root password is: kl3994aMsfkkeE
[INFO] Warning: Please delete the log files in /tmp/ispconfig-ai/var/log/setup-* once you don't need them anymore because they contain your passwords!

5.3 Setting up replication for Dovecot

We are going to use dsync to synchronise the emails between mx1 and mx2, for redundancy.

The custom settings for dovecot have to be stored in /usr/local/ispconfig/server/conf-custom/install/dovecot_custom.conf.master so you don't lose them when updating ISPConfig.

nano /usr/local/ispconfig/server/conf-custom/install/dovecot_custom.conf.master

Put the following in there:

protocol imap {
  mail_plugins = $mail_plugins quota imap_quota notify replication
protocol pop3 {
  mail_plugins = $mail_plugins quota notify replication
protocol lda {
  mail_plugins = $mail_plugins sieve quota notify replication
protocol lmtp {
  mail_plugins = $mail_plugins sieve quota notify replication
doveadm_password = /(:&p-J:4e%?\@Q-;VSE#3Dmfm[fVK&r-mx2
doveadm_port = 12345
replication_max_conns = 50

ssl_client_ca_dir = /etc/ssl/certs

# Replicator process should be started at startup, so it can start replicating users immediately:
service replicator {
  process_min_avail = 1

# The mail processes need to have access to the replication-notify fifo and socket.
service aggregator {
    fifo_listener replication-notify-fifo {
        user = vmail
        mode = 0666

    unix_listener replication-notify {
        user = vmail
        mode = 0666

# Enable doveadm replicator commands
service replicator {
    unix_listener replicator-doveadm {
        mode = 0666

# Create a listener for doveadm-server
service doveadm {
    user = vmail
    inet_listener {
        port = 12345
        ssl = yes
service config {
    unix_listener config {
        user = vmail

plugin {
    mail_replica =

Replace the doveadm_password with your own password - make it a long and random string for security reasons. It has to be the same on both servers.


mail_replica =

with your own hostname of mx1.

To apply these changes, copy the file to the dovecot folder and restart dovecot:

cp /usr/local/ispconfig/server/conf-custom/install/dovecot_custom.conf.master /etc/dovecot/conf.d/99-ispconfig-custom-config.conf
systemctl restart dovecot

5.4 Setting up synchronisation for Rspamd

Rspamd has a nice web UI. We are going to set up our servers as neighbours so you can view the settings, stats, and other data in one panel.

nano /usr/local/ispconfig/server/conf-custom/install/

Add these lines:

# Configuration from the ISPConfig template (must be updated if there are changes)
# Addrs local to this server.
local_addrs = [

# This list is generated by ISPConfig, place custom addresses/networks in
local_networks = "/etc/rspamd/local.d/";

dns {
    nameserver = [""];

# Custom configuration:
neighbours {
    mx1 {
        host = "";
        path = "/rspamd/";
    mx2 { 
        host = "";
        path = "/rspamd/";
# Last updated: 19-01-2022

Replace the hostnames with the correct hostnames for your main and secondary mail server. This config should be updated if the template changes, so make sure you verify this when updating ISPConfig.

Now we are going to add a website for this server in ISPConfig. Go to Sites -> Add new website and add the website "". Make sure you create this on the correct server ( Disable auto-subdomain, and enable SSL + Let's Encrypt. Then, go to options, and paste this in the Apache directives section:

RewriteEngine On
RewriteRule ^/rspamd$ /rspamd/ [R,L]
RewriteRule ^/rspamd/(.*)$1 [P]
Header set Access-Control-Allow-Origin

Replace with the hostname of the secondary nameserver.

Lastly, we have to enable some Apache modules and restart our services:

a2enmod proxy_balancer proxy_http
systemctl restart rspamd
systemctl restart apache2

Now we are going to set a password for the Rspamd UI on MX1, which we will use as Web UI for our Rspamd cluster.

Log in to ISPConfig as admin and go to System -> Server Config -> -> Mail -> Rspamd Password.

Enter a new password and click save. Then go to System -> Server Config -> -> Mail -> Rspamd Password and enter the same password there. Wait till the changes are propagated. When it's done, you can log in to Rspamd with your password at in your browser.

5.5 Securing the mailserver with a valid SSL certificate

For a working DSYNC and Roundcube setup, you need to have a valid SSL certificate in place for the used hostnames. This certificate can not be self-signed. If you are going to use additional hostnames for this server, like and, or if the installer could not create a valid certificate when installing, follow this guide to set up a valid certificate for your mailserver:

5.6 Setting up the firewall

Log in to the ISPConfig UI, and go to System -> Firewall. Then click "Add new firewall record".

Make sure you select the correct server. For our mailserver, we have to open the following ports:



No UDP ports have to be opened through the UI.

We are also going to open port 3306, which is used for MySQL, and port 12345, which is used for dsync, but only from our local network for security reasons. To do so, run the following command from the CLI, after the change from the ISPConfig panel is propagated (when the red dot is gone):

ufw allow from to any port 3306 proto tcp
ufw allow from to any port 12345 proto tcp

5.7 Mirroring MX2 from MX1 in ISPConfig

To finish the setup, you have to enable mirroring between mx1 and mx2. To do this, log in to ISPConfig, go to System -> -> "Is mirror of Server". Select and click save.

Our secondary mailserver is now installed. In the next step, we will install the main DNS server.

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By: Abacop

In "5.4 Setting up synchronisation for Rspamd" it says:

Replace the hostnames with the correct hostnames for your main and secondary nameserver.


I guess it should be:

Replace the hostnames with the correct hostnames for your main and secondary mailserver.


(Same issue as in 4.4)