TIdMessageEncoder = class(TIdComponent);

TIdMessageEncoder is a TIdComponent descendant that implements an encoder for RFC 2822-compliant message parts. 

TIdMessageEncoder provides properties and methods used to process RFC message header and body lines using either a file or a TStream descendant. TIdMessageEncoder is a base class that establishes the framework for Indy message encoders. 

TIdMessageEncoder descendants, like TIdMessageEncoderMIME, TIdMessageEncoderUUE, and TIdMessageEncoderXXE, further refine the message Encoder framework by implementing support for specific encoding schemes.