Last week, I looked at the features of PostPath collaboration server and its various components. As with all messaging and collaboration platforms, a certain amount of preparation must be performed to ensure seamless integration with the current working environment. Let’s run through the pre-installation checklist for PostPath and consider some of the more important requirements:

1. An Active Directory Domain, hosted by at least one domain controller, where the new server will reside


This is, of course, one of the most important requirements. Active Directory is a necessity for PostPath because of the way in which PostPath works. PostPath is designed to emulate a Microsoft Exchange server–as far as any other device on the network is concerned (including client applications and genuine Exchange servers). The assumption made by the creators of PostPath is that most organisations will already have an existing Microsoft Exchange environment in place. In order to make the integration of PostPath as painless as possible, PostPath uses information already stored in Active Directory by Microsoft Exchange. This enables mail services to be migrated to a Linux platform gradually, rather than in one giant leap.

For those not currently using Active Directory to manage their networks directory services, there is little hope unless adoption of Active Directory is considered. The deployment of Active Directory may give some the opportunity to explore the potential of a mixed-mode network: hosting directory services with Active Directory while providing Exchange-compatible collaboration via PostPath (on a Linux platform), and offering File Sharing services via Samba authenticating against the Active Directory (again from a Linux platform).


2. A working DNS (often provided by Active Directory Server ) and the IP address for the DNS server

Although the assumption made is that most people will be using Active Directory / Windows Server DNS services, BIND may also be used with PostPath.


3. Confirm that the server hardware where the PostPath server will be installed meets the minimum hardware requirements.

The minimum hardware requirements are quite reasonable. For under 500 users, PostPath recommend a minimum of one CPU (Pentium IV) with 1 GB of memory and 80 GB of hard disk space. Additional storage space should be allocated to hold the message store data.


4. A Linux installation of RHEL 4 (32 or 64 bits), CentOS 4.3 (32 bits), or SLES 9 SP1 (32 or 64 bits) with all required packages installed.

SLES and RHEL4 are the commercial distributions supported by PostPath; CentOS is a freely available clone of RHEL. It is recommended that a supported distribution be used in a production environment.


5. PostPath server software and license key

A free licence for up to 12 users is available from the PostPath website.  A sales representative should be contacted to discuss licensing for larger installations.


6. Recommended: Back up Active Directory before proceeding with the PostPath installation

A full backup of your organisations Active Directory database should be performed before installation of PostPath.  This is because PostPath will modify Active Directory while presenting itself to the domain as a Microsoft Exchange server. The backup should be taken via the Windows Backup wizard on your primary domain controller.


7. Identify whether the installation is to take place within an environment with Microsoft Exchange installed or not.

Note: Installation in an environment without Microsoft Exchange previously installed is not fully supported.

This is a very important requirement. Microsoft Exchange MUST be installed within your current environment in order to deploy a PostPath server. PostPath note that environments without a previous Exchange installation are not fully supported. One section of the installation process attempts to modify the Active Directory schema to enable installation in an environment with no existing Exchange servers. I have tried to get this to work several times but so far have had no luck.


8. Fixed IP address for the server where PostPath will reside

This is the domain for which PostPath will be handling mail. Example:


9. Fully qualified mail domain name for your mail service

This is the Active Directory domain. Example:


10. Active Directory Administrative Account Name and password with full Active Directory administration rights

11. A Windows Networking (NetBIOS) machine name for the new PostPath Server

This means a NETBIOS-compatible hostname for the server; this is also sometimes referred to as the short name. If the full name of the server is, the short name of the server is simply ‘postpath.’


12. File system configuration: PostPath strongly suggests the use of the XFS file system for the Installation data store. 

The recommended filesystem for hosting the PostPath message store is XFS with extended attributes enabled. Enabling XFP with extended attributes and quota support may require the building of system-specific kernel modules. The Installation guide includes a full and comprehensive set of instructions covering this process.

13. NTP (Network Time Protocol)

After installing the Linux OS on the machine that will be the PostPath server – make sure that NTP is running. NTP is required to ensure that authentication services to Active Directory function properly during installation.

The Linux system hosting PostPath should use ‘ntpd’ to synchronise its time with the Active Directory domain controller. Again, full instructions for configuring ‘ntpd’ are provided in the installation guide.

As you can see, there are quite a number of prerequisite requirements for the installation and operation of a PostPath server. While some of these requirements are either relatively simple to fulfil or fully documented, some may seem rather more demanding depending on your current infrastructure and network design. Those who are not currently using Microsoft Exchange or Active Directory will need to consider whether the functionality offered by PostPath justifies the deployment of Active Directory and what the potential advantages and/or disadvantages of introducing this may be.