ContentDescription is a string property used to represent the "Content-Description" Header field in a message part. ContentDescription provides the to associate some descriptive information with a given message body. 

For example, ContentDescription may be useful to mark an "image" body as "a picture of the Space Shuttle Endeavor." Such text may be placed in the optional ContentDescription property. 

ContentDescription is presumed to be given in the US-ASCII character set, although the mechanism specified in RFC 2047 may be used for non-US-ASCII Content-Description values.