Why are mail files in /var/mail owned by 'daemon' instead of the recipient?

The mail delivery agent /bin/rmail needs to be able to chown(2) these
files. It can not do so if you have removed the privilege CHOWN (see
setprivgrp(1m); removing CHOWN is recommended to prevent cheating on disk
quotas). To get around this, noting that /bin/rmail runs setgid to group
mail, you can grant privilege CHOWN to group mail only by inserting the
line "mail CHOWN" in /etc/privgroup. The change takes effect on the next
reboot, or immediately if you execute the command
"setprivgrp -f /etc/privgroup".

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