Thanks to the many, many people that wrote in (including two people from Microsoft, my brother-in-law Andy, and numerous others) with information about Exchange Server 5.5 Service Pack 2.
Service Pack 2 includes fixes to server issues that were previously made available as Microsoft Quick-Fix Engineering (QFE) patches. For a complete list of QFE patches included in this service pack, see Microsoft Knowledge Base article Q171593. Knowledge Base articles are available from the Microsoft support Web site.
Exchange Server 5.5 SP2 also includes a new features such as a Contacts Module for Microsoft Outlook Web Access, Outlook 98 for Win32 clients, a new version of Microsoft Outlook for Macintosh, a new version of Microsoft Exchange Chat Service, Microsoft Outlook HTML Form Converter, the Move Server Wizard and much more.
For more information, please check out the Microsoft Web site