Even though CrossBox is highly portable, make sure that your server satisfies the listed server requirements.

Supported Operating Systems 

CrossBox Server runs on any x86-64 (64 bit) Linux based operating system that has glibc version 2.17 and up.

Listed below are minimum required distribution versions. Versions equal to or greater than the ones listed below are fully supported:

  • RedHat/CentOS/CloudLinux 7
  • Ubuntu - 16.04 LTS xenial
  • Debian - 9 stretch
  • Fedora - 30
  • OpenSUSE - 15.1
  • Arch Linux
  • Slackware - 14.2
  • Gentoo
  • Mint - 18.3 sylvia

You can check you glibc version by running

ldd --version

via the command line interface.

Hardware Requirements 

CrossBox Server can run on a small virtual machine, a big dedicated server, or anything in between.

CPU and memory requirements vary depending on the version you'll be running, the number of enabled features, and the number of concurrent users.

Standalone Version

The standalone version comes with everything prepackaged and preconfigured. It is intended for installing and running on a fresh, clean server.

Bare-minimum (use only core features):

  • 1 CPU
  • 512 MB of RAM
  • 5GB of Disk Space

Following features require additional memory when enabled:

  • Anti-Spam - 250 MB of RAM
  • Anti-Virus - 600 MB of RAM
  • TURN/STUN - 50 MB of RAM
  • Document Converter (CDC) - 100 MB of RAM
  • TrustedLink (email assets SSL proxy) - 50 MB of RAM

To run a standalone version with all features enabled, we recommend you install CrossBox on a server with at least 1 CPU and 2GB of RAM.

Control Panel Version

It's common for servers that utilize a control panel to have many of the needed services like MTA, mail server, anti-spam service, and anti-virus already running and in place.

Therefore, when installing on a server that's running cPanel, DirectAdmin, or Plesk, we auto-detect and use the following services automatically:

  • MySQL
  • Exim
  • Dovecot
  • MailScanner
  • ClamAV
  • CSF
  • Firewalld
  • UFW
  • Solr

This effectively reduces the total memory needed for CrossBox to run to just 512 MB of RAM, when used alongside the control panel.

Supported Control Panels

cPanel, Plesk, and DirectAdmin currently have deep-integrations available. 

However, you can still use CrossBox with any control panel due to its plug and play nature, but unlike with the supported control panels, some functions are not automated and may require manual action.

Hardware Calculation 

If you want to calculate your CPU and RAM resources in advance, here are the numbers:

1CPU, 2GB RAM for 100 concurrent users.

For example, if your plan is to host 100 concurrent users, you'll need:

  • 1 CPU
  • 2GB RAM

If your plan is to host 200 concurrent users:

  • 2+ CPU
  • 4GB+ RAM

Software Dependencies 

You don't need to install any new software dependencies for CrossBox to work. It comes pre-compiled and runs isolated from the rest of the system.

It won't ask you to install anything via your system's package manager other than core packages like locale package etc. We do not interfere with other software/packages/libraries you may already have running on the server.


Most of the time firewall will be configured with what's installed on the machine. However, this may not be the case with custom firewall configurations. We only support CSF, UWF, Firewalld. If CrossBox is not accessible, but crossbox status says all services are running, the most common reason for limited connectivity is your firewall.

When installing panel version of CrossBox, these ports must be free:

100 - TCP IN/OUT CrossBox default port
443 - TCP IN/OUT
3478 -  TCP and UDP IN/OUT TURN
5349 - TCP and UDP IN/OUT TURN Secure
49152:65535 - UDP IN/OUT Port range for TURN

When installing standalone version of CrossBox, these ports must be free:

25 - TCP IN/OUT SMTP Local Delivery
80 - TCP IN/OUT CrossBox HTTP
100 - TCP IN/OUT CrossBox default port
443 - TCP IN/OUT CrossBox HTTPS
465 - TCP IN/OUT SMTP Secure
993 - TCP IN/OUT IMAP Secure
995 - TCP IN/OUT POP3 Secure
3478 - TCP and UDP IN/OUT TURN
5349 - TCP and UDP IN/OUT TURN Secure
49152:65535 - UDP IN/OUT Port range for TURN

If any of these ports are taken, the installer will likely fail. Make sure you disable/remove all services that bind to these ports.

Or if otherwise configured, as CrossBox allows custom ports in the configuration settings.

Master and Slave servers

Entire cluster must be able to communicate  with each other trough 80/443 and default 100 port (unless configured differently). If Master server cannot connect to slave servers, login and other services will not work.

Other Requirements 


Make sure that before installing CrossBox your server has a resolvable hostname.

PTR (Reverse DNS)

We recommend that the server has a valid PTR (Reverse DNS) record that matches the server's hostname. A valid PTR record is important for good e-mail delivery.

Most VPS/Dedicated server providers allow you to edit a PTR record via the control panel they provide. 

Root Access

A root user account and SSH access are required to install a CrossBox Server.

Web Terminal with root user access can also be used (for example WHM Terminal).

Home Directory

Your system needs to have a /home directory. If it doesn't exist, CrossBox Installer will automatically create it.

Let's start 

Are you ready to get started?
Continue to Quick Installation Guide and have CrossBox up and running in a couple of minutes.