Assume that your DisplayName property is blank in a Microsoft Exchange Server 2010 environment. Additionally, assume that Microsoft Outlook is running in ANSI online mode, and you have an online profile to receive email messages. In this situation, the Microsoft Exchange RPC Client Access service (Microsoft.Exchange.RpcClientAccess.Service.exe) crashes. Therefore, you cannot access your mailbox. Additionally, the following event is logged in the Application log on the Client Access server:
This issue occurs because a System.ArgumentNullException exception occurs in the DoesEncodingUseFallbackCharacters function.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.