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 220.127.116.1109 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:
Article ID: 2937628 - Last Review: 11 Nov 2014 - Revision: 1
Exchange Server 2010 Enterprise, Exchange Server 2010 Standard, Exchange Server 2007 Standard Edition, Exchange Server 2007 Enterprise Edition, Microsoft Exchange Server 2003 Enterprise Edition, Microsoft Exchange Server 2003 Standard Edition