Sun Java System Communications Services software is highly scalable. A March 2003 report from The Radicati Group [Messaging Total Cost of Ownership 2003 in Enterprise and Service Provider Environments, The Radicati Group, March 2003] stated that the average Sun enterprise deployment had more than 5000 users on each server; in contrast, Microsoft Exchange 5.5 deployments averaged just 477 users per server.
Sun Java System Communications Services software scales well due to its robust messaging component technology. The message store is optimized and scales exceptionally well. The message transfer agent (MTA) is arguably one of the most robust, feature-rich MTAs on the market, with over 20 years in Internet mail deployments. Its multithreaded design is optimized to enable maximum message throughput, making it ideal for mass mailing, rich content delivery, and unified communication services. Indeed, Sun Java System Communications Services are embedded in most of the voice mail, unified messaging, and multi-media messaging providers available today. The component technology and architecture of Sun Java System Communications Services software enables the quality of service expected by both IT administrators and end users.
Microsoft Exchange, designed to scale to the workgroup level, not the enterprise level, does not scale nearly as well as Sun software. This limited scalability prevents Microsoft Exchange from providing a compelling TCO story. Managing dozens or hundreds of Microsoft Exchange servers is cumbersome and leads to high software, hardware, and administrative costs.