There are sites that send future emails.
Whether they will exist in the future is unknown.
Setting file option. You can set preferences for the current file’s default layout, opening and/or closing scripts, login information, and spelling. To set preferences for all files, see Setting preferences.To set options for opening and closing the current file:1.Choose File menu > File Options, and click the Open/Close tab if it is not already selected.
No a date calculation can not generate an email. This can be done with a calculation field and a script to send email.
You would have duedate field, then you need a field with a date calculation for the notice date. Noticedate=duedate-5 would be the calculation.
You could have the program to check the notice date and send email every time you open the app or you could setup a button to check noticedate and then email a notice.