ReceiveStream is a TStream property that represents the destination for data received in the logging intercept. 

Applications must assign a TStream instance to the ReceiveStream property to allow logging for data received in the logging intercept. 

Set FreeStreams to True if the stream instance can be freed when Disconnect is called for the logging intercept. 

When the intercept is Active, data received by the logging intercept is written to ReceiveStream. No textual messages or date / timestamp values are written to ReceiveStream. 

Use SendStream to indicate the stream used for writing data sent on the logging intercept.

TIdLogStream.FreeStreams 

TIdLogStream.SendStream