You can check the BodyFormat property:
Delphi-Quellcode:
type
OlBodyFormat = TOleEnum;
const
olFormatUnspecified = $00000000;
olFormatPlain = $00000001;
olFormatHTML = $00000002;
olFormatRichText = $00000003;
For RTF and plaintext the body is in the body property, for
HTML and unspecified the body is in HTMLBody.