Outlook Mobile Access for Exchange 5.5 Reports "All CDO Sessions Are In Use (Default Is 300)" (297976)

IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry

SYMPTOMS

When using Outlook Mobile Access for Microsoft Exchange Server 5.5, you may be unable to browse your mailbox or a specific folder in your mailbox during high server usage.

In the Application log, you may see events that contain the following error message:

All CDO sessions are in use (default is 300)

RESOLUTION

To resolve this problem, increase the default number of Active CDO sessions.

On the Mobile Information Server on which the Outlook Mobile Access for Exchange 5.5 component is installed, increase the value of the following registry key: WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

Start Registry Editor (Regedt32.exe).
Locate the MaxActiveCDOSessions_Count value under the following key in the registry:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Oma55\CDOSessions
On the Edit menu, click String, type a value that is > 300, and then click OK.
Quit Registry Editor.

MORE INFORMATION

Microsoft Outlook Mobile Access for Exchange 5.5 uses Collaborative Data Objects or CDO to talk to the Exchange 5.5 server, the same mechanism as Outlook Web Access for Exchange 5.5.