All one have to do in Plesk to fix this problem is to add to the open_basedir “:/dev/urandom“. So it looks like this {WEBSPACEROOT}{/}{:}{TMP}{/}:/dev/urandom
This script go over all Qmail mailboxes and removes oldest emails from accounts that are over 250MB in size and removes 5MB worth of emails.
Works ok PLESK systems on CentOS. Read More