procedure TForm1.Button1Click(Sender: TObject);
begin
  Mail('mail@test.de', 'Betreff');
end;



procedure TForm1.Mail(const aRecipient, aSubject: String);
  const
  olMailItem = 0;
  cRTFText = '{\rtf1\ansi\ansicpg1252\deff0\deftab720{\fonttbl'  +
             '{\f0\fswiss MS Sans Serif;}{\f1\froman\fcharset2 Symbol;}'+
             '{\f2\froman Times New Roman;}}{\colortbl\red0\green0\blue0;}'+
             '\deflang1031\horzdoc{\*\fchars }{\*\lchars }\pard\plain\f2\fs20 '+
             ' Hier kommt ein \plain\f2\fs24\b formatiertert\plain\f2\fs20 '+
             ' Text.\par }';
  var
    MyOutlook : Olevariant;
    MyMail : Olevariant;
  begin
    try
      MyOutlook := CreateOLEObject('Outlook.Application');
      MyMail := MyOutlook.CreateItem(olMailItem) ;

      MyMail.To := aRecipient;
      MyMail.Subject := aSubject;

      MyMail.Display;

      MyMail.Body := cRTFText;

      MyOutlook := UnAssigned;
      MyMail := UnAssigned;

    except
      on E: Exception do
      begin
        MessageDlg(E.Message, mtError, [mbOk], 0);
      end;
  end;
end;