Exchange 2010 Enterprise: We have a shared email account that many people have full Access Permission to.
Looking at the list of messages in the Inbox, some (NOT ALL) of them have no information in the 'From' field unless the message is opened or selected for preview. As a test I gave myself full access permission to the account, and added it as a separate Outlook
profile, and it does the same thing to me so it's definitely something on the server side.