For some time I've been racking my brains about various ways to implement
Maildir quotas in situations where you cannot use filesystem-based quotas
-- such as when you use a virtual domain manager where all Maildirs have
the same uid/gid.
Before I waste any more time on this, I'm going to wait for a while and
give people a chance to poke holes in what I've came up with.
Here's what I'm thinking: http://www.concentric.net/~mrsam/maildirpp.html
It's a bit rough, needs to be rewritten in a more formal way, and cleaned
up a bit.