procedure TMainForm.Button1Click(Sender: TObject);
var
  smtp: TIdSMTP;
  ssl: TIdSSLIOHandlerSocketOpenSSL;
  msg: TIdMessage;
  log: TIdLogEvent;
  i: Integer;
begin
  smtp := TIdSMTP.Create(nil);
  ssl := TIdSSLIOHandlerSocketOpenSSL.Create(nil);
  msg := TIdMessage.Create(nil);
  log := TIdLogEvent.Create(nil);
  log.OnConnect := logConnect;
  log.OnDisconnect := logDisconnect;
  log.OnReceived := logReceived;
  log.OnSent := logSent;
  log.OnStatus := logStatus;

  smtp.Intercept := log;
  ssl.Intercept := log;

  try
    try
      log.Active := True;
      smtp.Host := 'smtp.gmail.com';// <- funktioniert

      // mail.gmx.net <- Problem authentifizierung

      smtp.Port := 587;
      smtp.Username := 'USERNAME@gmail.com'; // USERNAME@gmx.at
      smtp.Password := 'PASSWORD'; // PASSWORD

      ssl.Host := smtp.Host;
      ssl.Port := smtp.Port;
      ssl.SSLOptions.Method := sslvTLSv1;

      smtp.IOHandler := ssl;
      smtp.UseTLS := utUseRequireTLS;

      msg.Recipients.EMailAddresses := 'hans.mustermann@gmx.at';// irgendeine Test Adresse
      msg.Subject := 'This is the subject';
      msg.Body.Text := 'This is the body of the email....';

      smtp.Connect;
      smtp.Send(msg);
      smtp.Disconnect;

      Memo1.Lines.Add('*** email transfer successful ***');
      log.Active := False;
    finally
      log.Free;
      msg.Free;
      ssl.Free;
      smtp.Free;
    end;
  except
    Memo1.Lines.Add('*** email transfer not successful ***');
  end;
end;

procedure TMainForm.logConnect(ASender: TIdConnectionIntercept);
begin
  Memo1.Lines.Add('*** Connect ***');
end;

procedure TMainForm.logDisconnect(ASender: TIdConnectionIntercept);
begin
  Memo1.Lines.Add('*** Disconnect ***');
end;

procedure TMainForm.logReceived(ASender: TComponent;
  const AText, AData: string);
begin
  Memo1.Lines.Add(AText + ' REC: ' + AData);
end;

procedure TMainForm.logSent(ASender: TComponent; const AText, AData: string);
begin
  Memo1.Lines.Add(AText + 'SEND: ' + AData);
end;

procedure TMainForm.logStatus(ASender: TComponent; const AText: string);
begin
  Memo1.Lines.Add('*** Status: ' + AText + ' ***');
end;