Exchange 5.5 used Active Server Pages (ASP) to communicate with Exchange server computers using Collaboration Data Objects (CDO) 1.2 and MAPI. This required administrators to carefully monitor performance counter objects for bottlenecks. Exchange 2000 doesn't use MAPI to communicate with the Exchange server computer containing the user's mailbox, and ASP pages are no longer used for client access. Clients still access the Web component using HTTP, but the IIS hosting the component uses the Web store to provide access to the user's mailbox. This means you need to monitor only the standard operating system bottlenecks -- CPU, memory, network and disk. This also means that OWA 2000 scales well.
This was first published in May 2003