Creating a CrossBox Cluster


If you are a hosting or a mail service provider, or if you ever plan to have more than one CrossBox server, then we advise you to think about creating a CrossBox Cluster. Here we will explain how you should plan your deployment and what are the benefits of building a CrossBox Cluster.


  • Advertise a single IMAP/SMTP/POP3 for all customers, no matter what specific slave server they are hosted on.
  • Advertise a single App URL for all customers, no matter what specific slave server they are hosted on. For example, you may have multiple cPanel/Plesk/Stand-alone servers and you wish to provide all customers from those servers with a single link.
  • Mix different cPanel, Plesk, and Stand-alone servers within the cluster.
  • Manage all servers from the Master's Admin Area.
  • Scale indefinitely by simply adding more Slave servers to the Master server.

Master-Slave(s) Topology

As you can see in the picture below, there is a single Master server with multiple Slave servers attached to it. You are free to mix any combination of cPanel/Plesk/Stand-alone servers within the cluster.


Building a CrossBox Cluster

First, install a Master server, log in to Admin Area and then add Slave server(s).

Master Server

This server is used to resolve domains and email addresses to your slave servers (where they are actually hosted) and it acts as a "visible" entry for all your customers.

For example, this is where would reside. 

However, the master server does not do any heavy work and it just delegates everything to the slave server which is resolved for that hosting account. Because there is no heavy work happening on the master server you can install a CrossBox Master on a small dedicated server or a VPS (Virtual Machine).

Note: You can also create fully workable CrossBox accounts on the master server itself.

Installing a CrossBox Master Server

Pick a small dedicated server or a VPS and install CrossBox as explained in a Quick Start Guide.

Slave Server(s)

These servers hold all your customer's CrossBox data and do all the work related to the activity of CrossBox accounts that are hosted there.

You can install a CrossBox Slave Server on a cPanel server, a Plesk server or a Stand-alone/Bare metal server.

Adding a Slave Server to the Master Server

Add new servers to your CrossBox Cluster in under 5 minutes.

To add a slave server to your CrossBox Master Server, please log in to the Admin Area of your CrossBox Master Server and click on the "Servers" icon. The list of all your CrossBox servers will appear. In the bottom right corner click on the  +  fab button.


Here you will be instructed to log in via SSH to the slave server that you wish to add. After you have successfully logged in as root, please issue the following command:

sh <(curl || wget -O - --slave 

Now just copy the URL that the command outputs, paste it in "Installer URL" box below and click "Add Slave" button. This will start up the installation wizard of CrossBox on the targeted server and you'll be able to complete the installation from the master's Admin Area. You can tweak all the CrossBox Options during the installation to customize the settings for that particular server. After the installation is completed, the added server will now be a part of your CrossBox Cluster.