Applies to: Exchange Online | Exchange Server 2007 | Exchange Server 2010 | Exchange Server 2013 | Office 365
The ContentId element represents an identifier for the contents of an attachment. ContentId can be set to any string value. Applications can use ContentId to implement their own identification mechanisms.
The schema that describes this element is located in the EWS virtual directory of the computer that is running MicrosoftExchange Server 2007 that has the Client Access server role installed.