Hello,
You can't do it in Online form, but did you tried do disable the notifiaction email and do it manule through the event handler ?
CMS.OnlineForms.BizFormInfo.TYPEINFO.Events.Insert.After += Insert_After;
then in the function
private void Insert_After(object sender, CMS.DataEngine.ObjectEventArgs e)
{
CMS.OnlineForms.BizFormItem bi = (CMS.OnlineForms.BizFormItem)e.Object;
if (bi.BizFormClassName == "yourbizformclassname")
{
//make loop throught the notification emails and send them email separetly
}
}