I've increased the PM's per message folder to 25. (the default was 15, of course)
All users can still create 4 additional personal message folders - this is unchanged from before.
And all users can designate one of those personal folders to be an "inbox overspill" - new PM's will go there if the main inbox is full.
I'm hoping that PeterT won't mind the extra space used, considering where we used to be, and how many users are active these days.
I suggest creating a personal folder for long term storage, and move any messages you want to keep long term into that, to keep the main inbox clear.