Looking for ways to raise Postal Service revenue, the Trump administration has proposed a fundamental change to your mailbox: selling access to it to private companies.

The Postal Service could capitalize on a “highly valuable” asset by selling mailbox access to companies such as FedEx Corp. FDX, -0.82% and United Parcel Service Inc. UPS, -0.21% , the administration said in a report last week.

Read:Proposed U.S. Postal Service price hikes could hurt Amazon earnings

The Postal Service has been losing money for years as letter volume has declined and it has struggled with requirements that it fund retirement benefits decades in advance. It reported a net loss of $3.9 billion in the fiscal year ended Sept. 30.

Past proposals to boost revenue have ranged from privatization to the introduction of banking services—ideas last week’s report didn’t endorse. The report was commissioned in April by President Trump, who has regularly claimed that Amazon.com Inc. AMZN, -4.12% gets a sweetheart deal on package shipping from the Postal Service. It drew immediate attention for another proposal, tiered pricing for packages, which would likely raise shipping prices for e-commerce.

The proposal to license access to mailboxes was one of the ideas for using existing assets to find new revenue.

An expanded version of this report appears on WSJ.com.

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