My customer has CDOEX based legacy application which pulls the calendar and appointment items. Later they had merged their Exchange Server 2003 SP2 along with Exchange Server 2007 SP1 – mixed mode environment. He had an unique issue, whenever he tries to access couple of appointments created in Exchange Server 2007 environment, his CDOEX application throws the error : 8004011B: Unknown Error which means MAPI_E_CORRUPT_DATA.
When we started troubleshooting we found that those appointments were created using their Exchange Web Services(EWS) using their .Net application were throwing the error. We found the support KB which has the resolution. It’s because the appointments has the culture property and its value as “en-US”. Per the support KB, we recommended the customer to update with Update Rollup 5 for Exchange Server 2007 SP1. After updating the Exchange Server 2007 we found the issue got resolved.