I have added a quota feature for virtual email domain. This is settable
per domain (all users sharing the same limit). The default is not limit (0
means no limit). This is enforced in vdeliver. It is not relying on kernel
quota feature because generally vdomain users are sharing the same UID
space (by default, changeable). It was easier to handle it this way.
This feature can be controlled from the command line when creating
a new virtual email domain with the --quota option. See the linuxconf --help
to see the syntax. I still have to complete the help about this topic.