The United States Postal Service announced that it is “contemplating amendment” of its mailing standards for domestic mail, changing the standards for letter-size and flat-size pieces.

According to the release in the USPS Federal Register, the change would limit all mail that is shipped as Marketing Mail, “regular and nonprofit, letter-size and flat-size, to content that is only paper-based/printed matter; no merchandise or goods will be allowed of any type regardless of ‘value.’”

This means that, for sending marketing materials other than direct-mail pieces and other paper products, companies would have to use other USPS shipping methods, such as the normal priority mail method.

The USPS statement says:

The limitation to non-merchandise, paper-based/printed matter content would serve three goals: (1) Facilitate levels of service expected for the processing and delivery of merchandise that include end-to-end tracking and visibility, (2) move fulfillment of merchandise and goods out of USPS Marketing Mail, consistent with the transfer of fulfillment parcels out of Standard Mail (the predecessor to USPS Marketing Mail) in Docket No. MC2010-36, and (3) reduce operational inefficiencies when machines are unable to process letter-size or flat-size shaped inflexible items.

It added that moving other physical marketing materials from the letter-size and flat-size categories would improve the USPS’s processing capabilities and shifts the items to mail streams with better end-to-end tracking capability “consistent with marketing expectations.”

It also said that the switch would make letter-size and flat-size mail be delivered in a more efficient way.

A move from Marketing Mail to other services like Priority Mail would cause a headache for companies, as it would likely be more expensive.

The Nonprofit Times reported that the Alliance of Nonprofit Mailers (ANM) challenged the move in a letter to the USPS. The letter claims that the USPS doesn’t have the legal authority to regulate what nonprofit companies and fundraisers can put in envelopes. Stephen Karney, executive director of the ANM said it would “have a huge negative effect on nonprofits,” and “would rule out all front-end and back-end premiums that nonprofits have been sending for years.”

The USPS, in response, basically said not to worry just yet.

“This is not a notification of a change,” a USPS spokesperson told the NonProfit Times. “It is to gain feedback from mailers on this proposal.”

The USPS reported that comments on it are due by Oct. 22, 2018. If other mailers feel the same way as the ANM, the switch could never come to fruition.