This article describes what you need for a typical OX App Suite Setup for up to 1.000.000 Users, which is fully clustered, high available and scaling very flexible.
It contains everything you need to:
The system is designed to provide maximum functionality and availability with a minimum of necessary hardware. If the services on one OX server fail, this is transparently handled by the load balancer. If one MySQL server fails, it is sufficient to take over the IP address on the other MySQL server in the cluster to stay fully in operation.
To deploy the described OX setup, the following steps need to be done.
The following steps need to be done in every case to get OX up and running:
MySQL will be configured as Master-Master configuration to ensure data consistency on both servers. If one machine fails, the other machine will take over all functionality.
OX will be installed on minimum two servers. It will be configured to write to the first MySQL database and to read from the second MySQL database in one cluster. This will distribute the load during normal operation as smooth as possible. During FailOver the IP address of the failed MySQL server will be taken over to the working server, the system stays operable.
The NFS server will be mounted on all machines and registered as filestore.
When multiple Open-Xchange Servers are configured within a cluster Session and Loadbalancing needs to be set up.
You also should install and configure the OXtender for Business Mobility:
Let your users connect to their data from other services like Twitter or LinkedIn by configuring the "SocialOX"
The following components need to be implemented in your environment.
A load balancer in front of the OX servers is necessary for this deployment size. It needs to handle the requests if one OX server fails.
If you already have a hardware load balancing solution in place, this can be used. OX is known to work with the standard load balancing solutions from BigIP, Barracuda, Foundry, ...
If you do not have a load balancing solution already in place, we recommend to use Keepalived as reliable and cost effective solution.
Read more about configuring Keepalived for Open-Xchange
You need a Control Panel to create and edit users.
OX is designed to integrate into every solution you may already run in your environment and also into wide spread solutions, like the Parallels Control Panels.
If you do not run hosting services today and do not have a Control Panel in place, it is recommend to use Plesk to manage OX. With that combination you will get a full functional hosting platform containing everything you need.
If you already have a Control Panel in production, you should integrate OX with it. It is recommended to use the SOAP provisioning Interface for that purpose.
Read more about: Provisioning using SOAP
A good start to test and to understand the necessary commands are the Command Line Tools. They have exactly the same calls like the SOAP API.
Read more about: Open-Xchange CLT
Parallels Operations Automation (POA) is an operations support system (OSS) for service providers, who want to differentiate their offerings in order to reduce customer churn and attract new customers. Additional, the APS package adds a high performance, best in class email service to Parallels Plesk Panel customers.
To avoid password synchronization issues, it is recommended to use your existing email authentication mechanism within OX. Then you do not need to add user passwords to OX, you simply use a plugin to authenticate against your IMAP server.
Read more about the IMAP Authentication Plugin
Other IMAP servers need to be tested thoroughly before going into production.
There are several possibilities to implement the Email system:
If you want to setup a new Email system based on Dovecot, it is recommended to use NFS as storage backend and to install at least two Dovecot servers, accessing this storage. With that setup you have best scalability and high availability with a minimum of complexity and hardware.
Read more in the Dovecot documentation including a QuickConfiguration guide
You will find plenty of additional documentation for customization of OX in our knowledge base 
When the main setup is completed, we recommend to start with the following articles to enhance your system and to become more attractive for your users.
It is recommended to implement at least a minimal monitoring/Statistics solution to get an overview of the systems health. If you have a support contract with Open-Xchange, it is very helpful, if the support can access the monitoring graphs. There are example scripts for a basic monitoring with [Munin] available.
Read more about installing and configuring Munin scripts for Open-Xchange
It is recommended to run regular backups for your OX installation. This can be done with every backup solution for Linux.
Read more about Backup your Open-Xchange installation