jwolthuis - 11:25 am on Dec 10, 2012 (gmt 0)

The lady at the post office told me the same thing

Are you referring to the padded envelope? The padded envelope doesn't have a "fold" like the cardboard envelopes do. they are made from Tyvek, and both short ends are "continuous", with no fold. The long sides are sealed together, but again don't form a "fold", more like a seam.