A lot of people claim they send bubble mailers as regular envelopes and nobody stops them. Some people report that they have received bubble envelopes with postage due - sometimes they are even charged the priority mail rate.

Postal regs (which many postal employees do not enforce) say a bubble mailer is not a regular envelope because it is either too thick (more than 1/4 inch) or because it contains a rigid item (a chip) instead of something that can flex its way through the automatic sorting machines.