That is the phrase that strikes fear into the heart of every mail carrier.
Consider for a moment the amount of mail you get in one day. Now, multiply that volume by 550 (the number of boxes on my route). Try to imagine how that pile of mail would look... neatly sorted and placed into trays, of course. That is a conservative estimate of how much mail I have to move in an average day. It is conservative because I have something like 40 businesses on the route, four of which get enough mail to fill a foot high tub.
Okay, now. Take your sorted day's worth of mail and mulptiply that by three.
If you can visualize that, you have will begin to get an idea of what I did today.