Encode is an overloded procedure in TIdMessageEncoder that retrieves the un-encoded values of an RFC 2822-compliant message part, and constructs the encoded contents of the message part. 

ASrc is a the stream used to retrieve the un-encoded contents of the RFC message part. 

ADest is the stream where the encoded message part will be written. 

The Stream-based variant of Encode is an abstract virtual procedure, and specifies the interface for using TStreams as bothe the source of the RFC message part and the destination for the Descendant classes, like TIdMessageEncoderMIME, TIdMessageEncoderUUE, and TIdMessageEncoderXXE, must implement the Encode method to provide support for genmerating the encoded message part contents using a specific encoding algorithm.

TIdMessageEncoderMIME 

TIdMessageEncoderUUE 

TIdMessageEncoderXXE 

TIdMessageEncoderQuotedPrintable 

TIdMessageEncoder.Encode