Email Reminder Feature

Please, PLEASE, incorporate the old feature to email recipients at predetermined times (like the ‘sound’ event) into the new version. I have several instances where I would like an email sent to people (not when I create the event, but e.g. 1 day before) to remind them that they have (for instance) a hospital visit to attend ‘tommorrow’. The only current means available (anymore) is to send an email when the event is created. An email 1 day (and perhaps an additional email 2 hours before) an event would help remind the recipient of an important scheduled event in the calendar. Please… I really like thunderbirds features and don’t want to start all over with a different calendar software that provides this option. (-or- perhaps just run an external program / batch file where several options could be implemented ?)