lues specified
 by RFC 2045 are "7bit", "8bit", "quoted-printable", "base64", and "binary".
 <p>
 For example, a <code>FileDataSource</code>
 could be created that forces all files to be base64 encoded:
 <blockquote><pre>
  public class Base64FileDataSource extends FileDataSource
                                        implements EncodingAware {
        public Base64FileDataSource(File file) {
            super(file);
    }

        // implements EncodingAware.getEncoding()
        public String getEncoding