Internet Direct (Indy) Version 9.0.1 Beta
TIdMessagePart.IsEncoded
Indicates that the body for the message part is MIME-encoded.

property IsEncoded: Boolean;
Description
IsEncoded is a read-only Boolean property that indicates the body of the message part is stored in MIME-encoded form. IsEncoded normally reflects that the body contains a graphic image or BASE64 or QUOTED-PRINTABLE encoded value.