SBS Err Msg: Unable to Display This Folder (192712)

CAUSE

During the logon process from a client to the server, there are three connections that are made: one for the actual client (Outlook or Exchange) and two (see NOTE below) for the MAPI spooler. The client connects first and creates a mapped file with the name derived from the server that it is connecting to. The information contained in this file allows multiple connections to be linked and only count as one user. When the MAPI spooler logs on and tries to open this mapped file created by the client connect, the open failed because the file handle was erroneously closed.

This caused the MAPI spooler to create a new mapped file and, therefore, incremented the user count to 2 for every client logon attempt. The MAPI spooler then makes a second connection to the server and tries again to open the mapped file created by the client connect. This open failed as well, leading the MAPI spooler to create yet another mapped file and, therefore, incrementing the user count to 3 for every client logon attempt. As a result, using a 5-user license for Small Business Server would only allow 2 Outlook or Exchange client logon attempts before running out of licenses.

NOTE: The MAPI spooler opening 2 connections to the server was introduced in Exchange Server 5.5 SP1; previous to this, it only opened one. So the number of user connections seen as a result of this problem may fluctuate between 2 or 3, depending on client versions. The number of User Connections can be seen by using Performance Monitor and selecting the User Count counter under the MSExchangeIS object.