Scheduling emails is not yet widespread. I schedule emails for the beginning of work day so that peope do not get beeps when they sleep or feel pressured to answer if they don’t, and some people presume I am working hard at 8 am … Before pareve milk was not widespread, you were supposed to keep the package on the table.
There is also an issue of asking someone to do an action, starting from reading your email, responding, or doing some activity you asked for.
The easiest case is sending to a shomer shabbos Jew in another time zone and let him deal with whatever you need.