I just noticed that this is templated too, though it seems to be done a little differently from regular ones. You should copy the /etc/e-smith/templates/home/e-smith/.qmail file to /etc/e-smith/templates-custom/home/e-smith/.qmail and change the $local_delivery value near the beginning to the "| /usr/bin/procmail ~/.procmailrc" line to use procmail. If you don't use the templates, it'll be wiped out with a reboot, just like everything else.