I did some google searching and didn't see any easy/obvious way to turn on quota reports in Horde.
I dreamt up a cron script you could use, though:#!/bin/bash
todom=`/sbin/e-smith/config get DomainName`
cd /home/e-smith/files/users
for u in *; do /usr/bin/quota -u $u |/bin/mail -s Quota\ Report $u@$todom; done
* Create /etc/cron.daily/quota_report.sh
* Add the content shown above
* set it to be executable ("chmod +x /etc/cron.daily/quota_report.sh")
Your users should now get daily emails showing their quota.