You can obtain "solid" or rigid paper envelopes for FedEx shipments through several channels, often for if you are using specific expedited services. Where to Get FedEx Envelopes
: Sells individual or bulk rigid board photo/document mailers in-store. buy fedex envelopes
FedEx Office locations, ship centers, or even from supply cabinets at FedEx Drop Boxes. You can obtain "solid" or rigid paper envelopes
: Sites like Amazon and Alibaba sell bulk packs of compatible heavy-duty cardboard mailers. Top Recommended "Solid" Envelope Options Shipping, Packing, and Mailing Supplies - FedEx and Mailing Supplies - FedEx