How much Mail is delivered per Prisoner?

Solution 1:

Although this isn't answering your direct question about how much mail per person arrives, I think that even 35 mail delivery people can be way too few if your "Work/Free Time" is scarce for a prison of that size. Mailroom workers take a long time to deliver a single piece of mail, and if the path is long enough, might not even get through a single satchel of mail in a single work hour. I'd either increase the number of workers in the mail room(s) or create more Work time in the daily regimen.

Mail (along with phone access and visitation) is very important in keeping the Family need in check. Screwing with prisoners' mail is a good way to get them all riled up.