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PostPath Provides MS Exchange Pain Relief

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PostPath: Linux-based Exchange-compatible e-mail and collaboration server.

Planning a move away from Exchange can be almost as painful and expensive as staying with it. With PostPath, it’s possible to avoid both pain points.

System administrators seeking an alternative to Microsoft Exchange, be it for cost or interoperability reasons, will find PostPath e-mail and collaboration server to be the current pick of the litter.

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Replacing Exchange is a formidable task: The cost must be reasonable, all the functions that users have come to expect must be included, it must use a sane data storage format, be easy to backup and restore, it must be scalable from small shops to giant enterprises, migration must be reasonably uncomplicated, and, perhaps most important of all, because users demand it, the application must support MS Outlook.

There are a host of excellent mail, messaging, and groupware servers, many of them open source and free of cost, but the three main sticking points are migration, Outlook support and Active Directory integration. The fragile, closed proprietary data stores that MS Exchange and Outlook use make migration difficult and imperfect, and Microsoft’s closed proprietary protocols make supporting Outlook and mobile devices difficult.

Messaging and groupware suites that target the enterprise, like Open-Xchange and Zimbra, deal with client support in two ways. Some use AJAX-based Web interfaces, which have the advantages of being cross-platform and standard-compliant, so it’s easy to deliver full functionality to all users on all platforms. Others use special connectors for Outlook support at added cost. Data migration involves extra expense and special expertise. So it’s no wonder that planning a move away from Exchange is almost as painful and expensive as staying with it.

The PostPath folks took a different and more difficult route. They chose to implement Exchange’s own protocols. This meant using both the available public documentation and reverse-engineering the undocumented bits by decoding what went over the wires. This is a tedious, time-consuming business, but the result is a groupware and messaging server that is a genuine drop-in Exchange replacement. To Active Directory, Outlook and other Exchange servers, it looks just like an Exchange server.


Like Exchange, PostPath requires Active Directory. Your DNS must be in order, plus NTP and NetBIOS. It needs 20GB of storage for system files, as well as adequate space for a data store and enough horsepower to handle whatever loads are put on it. The PostPath folks recommend at least a P4 CPU and a couple of gigabytes of RAM. It is supported on Red Hat Enterprise Linux 4.4/4.5, both 32- and 64-bit, 32-bit CentOS 4.4/4.5, and SUSE Linux Enterprise Server 10, 32- and 64-bit.

Installation is the hairiest part. It’s a fairly complex process that requires the usual twiddling to introduce it to Active Directory. The PostPath installer itself is straightforward and helpful, and there is a detailed installation manual. In fact, there are reams of good documentation and manuals. I tested it on both Windows Server 2000 and 2003, running Exchange 2000 and 2003. There are special issues with Exchange 2007 that are covered in the documentation.

Some older reviews still floating around on the Web say you must have Exchange before you can install PostPath. This is not true — you can start from scratch and install PostPath into an Active Directory domain without having an existing Exchange server.

Easing On In

Testing PostPath on your network is safe. Start by testing it with a single user, and gradually migrate more at your own speed. PostPath just looks like another Exchange server, so there is nothing to alarm the natives. If you’re not experienced with running a Linux server, take it slow. PostPath is very different from Windows. In my opinion, it’s a lot more straightforward and sane. Old Unix admins should feel right at home.


PostPath is based on Linux, Postfix, Samba and other nice efficient open source applications, so you get a lot more bang for your buck. PostPath contributes patches and extensions to several OSS projects. It uses standard Linux journaling filesystems (you get to pick your own favorite filesystem), and the data store uses plain old ordinary Linux files and directories. Each message lives in its own separate file, rather than being lumped into a single giant database file. Total storage requirements are considerably smaller.

In other words, you don’t have to devote significant hardware resources to a product that can barely get out of its own way, and you can instead apply them to actually doing productive work. Not surprisingly, PostPath claims as much as 100 times faster performance.

Backups and restores are done with standard utilities and don’t need any special handling. Single messages are easily retrieved, and if one message becomes damaged it will not corrupt the entire store. Linux is immune to the torrents of Windows malware roaming the Internet, and you can use any virus-filtering application that you want instead of being limited to special Exchange-capable applications. Thus, it’s easier to secure.

There are also special tools for high-availability, replication and integrating remote locations.

In my own testing I found nothing remarkable to report — once I got through installing PostPath, it just did its job. Well, actually that is remarkable, at least to battle-scarred Exchange admins.

PostPath offers 30-day 12-user free trial downloads, either PostPath-only to install on existing Linux systems, or a complete VMware edition to install on a Windows machine. The VMware edition eats up more system resources, so be sure to take that into account. PostPath claims its licensing costs are around one-fourth that of a typical Exchange installation. Factor in easy migration, lower hardware requirements, easier administration, and it’s an attractive package.

Reviewed by: Carla Schroder
Original Review Date: 04/18/2008
Original Review Version: 2.4

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