The U.S. Postal Service is reminding businesses making vape components to be ready for new prohibitions on mailing their products.

A ban taking effect next week could apply to all vape companies, even those shipping legal hemp-derived products. The ban was adopted late last year to reduce access to vape products and could eliminate direct-to-consumer vape shipping.

The Postal Service reminded the industry of the looming ban in a federal notice Monday. The agency pointed out that companies could ask for exceptions to the ban but gave no indication whether they’d be making any exceptions.

Several hemp and marijuana vape operators have said the change will severely harm their businesses.

FedEx and UPS already have said they will follow the U.S. Postal Service’s directive and won’t ship vaping products.

The Postal Service added a pointed reminder that it is free to enforce federal marijuana prohibition and that products containing any THC can’t be mailed. The agency also gave hemp shippers a reminder to keep all their paperwork handy.

“Mailers must retain, and prepare to make available upon request, records establishing compliance with all applicable federal, state, and local laws pertaining to hemp production, processing, distribution, and sales,” the notice said.