iptables, /proc/modules: No such file or directory

==== Required information ====
- iRedMail version: 0.8.7
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Linux/BSD distribution name and version: Ubuntu Server
- Related log if you're reporting an issue:
====

iptables, which was set up by iRedMail, can't find /proc/modules, and this is because I installed Ubuntu Server using my host's install image, which uses a non-modular kernel. Which config file should I edit to change IPTABLES_MODULES_UNLOAD?

I'm thinking I have a problem similar to this: http://forum.ovh.co.uk/archive/index.php/t-4280.html