Macintosh Clients Hang When the Exchange Server Is Busy or Down

• Microsoft Exchange Macintosh client, versions 4.0 and 5.0
• Microsoft Outlook Macintosh client, Exchange Server Edition, version 8.0

SYMPTOMS

The Macintosh computer appears to hang after a period of time with the Exchange Client running.

CAUSE

The current revisions of the Exchange Macintosh client use polling to check for mail (at approximately 70-second intervals) and not push notification. The networking calls for this polling are via synchronous RPC calls (as all Exchange clients are). This means that if the request is not responded to (either because the server is down or very busy) the process will wait. This is why the Macintosh computer hangs, or appears to hangs. A cooperative multi-tasking operating system like the Macintosh, Windows, and Windows For Workgroups blocks the synchronous calls until responded to. This behavior exists in the Windows 95 and Windows NT Exchange Clients, but is not a problem because they use preemptive multi-tasking, which hangs the Exchange session without disturbing other running applications.

WORKAROUND

The Microsoft Outlook 8.0 Client for Macintosh has been modified to prevent this behavior by implementing a timeout parameter that resets and clears the client polling communications call with the server, if it does not receive a reply within a period of time. This is only available for Power Macintosh computer.

MORE INFORMATION

For more information on the Outlook Client for Macintosh version 8.0, please see the following Microsoft Knowledge Base article:

   ARTICLE-ID: Q178124
   TITLE     : Microsoft Outlook for Macintosh and Windows 3.1x

Keywords          : XCLN
Version           : MACINTOSH:4.0,5.0,8.0
Platform          : MACINTOSH
Issue type        : kbprb
Solution Type     : kbworkaround