RawHeaders is a read-only TIdHeaderList property that contains the message header names and values in their original form, as received in an HTTP request or response. 

RawHeaders are used as the origin for header values during processing and storage in their property representation. RawHeaders are used as the destination for property values when generating the headers for an HTTP protocol response. 

Use CustomHeaders to create new header values that cannot be expressed as a property in the TIdEntityHeaderInfo instance.

CustomHeaders 

TIdHeaderList 

TIdRequestHeaderInfo 

TIdResponseHeaderInfo