When you retrieve an email attachment by using an Exchange Web Services (EWS) application, the ContentID element does not follow the order that is dictated by the XML schema. Specifically, the ContentID element may be returned as the last property instead of following the order of the elements. Therefore, EWS cannot identify the attachment.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
The protocol schema defines that the properties should be returned in the following order in the AttachmentType complex type:
Article ID: 2931842 - Last Review: May 27, 2014 - Revision: 1
Microsoft Exchange Server 2010 Service Pack 3, Microsoft Exchange Server 2010 Enterprise, Microsoft Exchange Server 2010 Standard