TIdDecoderMIMELineByLine = class(TIdDecoderMIME);

TIdDecoderMIMELineByLine is a TIdDecoderMIME descendant that implements a specialized MIME (or Base64) decoder. It is used primarily when handling MIME-encoded mail messages. 

WARNING: This is not a general-purpose decoder. It is used, for example, by IdMessageCoderMIME for line-by-line decoding of base64 encoded parts that are processed on a line-by-line basis, as against the complete encoded block. If you use it, you must call Clear before the first line, and also call CheckForLeftOvers after the last line.