MAPI/CDO client cannot connect to Exchange servers when a network event occurs


Assume that a client application uses Microsoft Exchange Server MAPI Client and Collaboration Data Objects (MAPI/CDO) version 1.2.1 to connect to a Microsoft Exchange Server 2010, Exchange Server 2007 or Exchange Server 2003 server, and the version of Exchange MAPI/CDO update is or an earlier version. When a network event occurs, the client cannot connect to the server to sync email items.


This issue occurs because connection handle leaks occur on the client for each network event so that MAPI sessions are not actually closed and they keep connecting to the server. When the number of MAPI sessions reaches the limit of the server, new connections cannot be built. 


To resolve this issue, download and then install Exchange MAPI/CDO 1.2.1 March 2014 Update from the following Microsoft website:

Note The version of this update is 6.5.8353.0.


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

More Information

For more information about how to use MFCMAPI to create a MAPI profile to connect to Exchange 2010, go to the following Microsoft website:For more information about Exchange MAPI/CDO update (version:, go to the following Microsoft website:

Article ID: 2937628 - Last Review: Nov 11, 2014 - Revision: 1