Consider the following scenario. You connect to a Microsoft Exchange Server 2010 Client Access server by using an Internet Message Access Protocol (IMAP) client. You use the FETCH (BODYSTRUCTURE) command to query information about an attachment of an email message. In this scenario, the file name of the attachment may contain the "?" character.
This issue occurs because the file name of the attachment contains double-byte character set (DBCS) characters. Exchange Server 2010 does not return a RFC compatible response when the file name of an attachment contains DBCS characters.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.