Waterproof Corrugated Mailer Cosmetic Packaging Box This waterproof corrugated mailer cosmetic packaging box is engineered for the realities of online beauty retail, where parcels are stacked, tossed and sometimes left in the rain. E flute corrugated board cushions glass bottles, jars and palettes against impact, while a waterproof varnish shrugs off moisture during transit and storage. The self-locking mailer folds from a single blank into a sturdy, tape-free parcel,