Assume that you use a MAPI client such as Outlook 2003 in online mode in a Microsoft Exchange Server 2010 environment. When you send an email message, the Microsoft Exchange RPC Client Access service might crash on the Exchange Server 2010 Client Access server. Additionally, the following log is logged in the Application log:
Note When the issue occurs, Outlook users in the domain are disconnected from the Exchange server.
This issue occurs because the RPC Client Access service does not validate the recipient data before the service processes the data. Therefore, when the recipient data that is stored in an invalid format is processed, a System.ArgumentException exception occurs, and then the service crashes.
To resolve this issue, install the following update rollup:
2645995 Description of Update Rollup 1 for Exchange Server 2010 Service Pack 2