May one leave one’s computer on over the weekend with the knowledge that an email will definitely be sent on Shabbat. What about if one is downloading a large file which started on Friday but will almost inevitably carry on downloading over the Shabbat?
There are two problems: 1. Is there any Chilul Shabbat done throughout the process: Was the source ready before Shabbat? Do the communication companies not work on Shabbat? 2. The use of automation on Shabbat. Rav Moshe Feinstein's opinion is that it can cause a breach in the Shabbat system. We use automation on Shabbat only where there is a great need, or things we were used to before there was automation, by assistance of Goyim etc. Anything new would need to be studied and cheked if it won't be a precedent to things we will be sorry of later. Rabbi Ya'akov Ariel