Yes, can we, to like 1 minute maybe, not six!! If you worried about space on the server or something, just keep the inbox max to ten, I would be happy with that..
Nah... there wouldn't be as many PMs as posts being sent through the server anyway.
It's not a matter of who sends what when it comes to the cap, its more or less when you have multiple PMs to respond to at once and you don't want to wait six minutes between each and every message.