Amazon is in the middle of a 60-day trial in which it’s relying on the US Postal Service to deliver groceries from its AmazonFresh service to select residents in the San Francisco area. Specifically, the postal service has been delivering small grocery parcels in insulated bags to customers’ doorsteps between the hours of 3 am and 7am – a time when demand for delivery is at its lowest.

If successful, Amazon may consider expanding the service nationwide according to a spokesperson from the postal service. Their goal at this point is to determine if delivering groceries would be feasible from an operations standpoint and if it would be financially beneficial.

It’s no secret that the US Postal Service has been dealing with declining mail volumes for years. The Internet has changed the way we communicate as a country which means our reliance on the postal service has waned – it’s one of the reasons they adopted a five-day delivery schedule for mail last year.

Package delivery, on the other hand, is a completely different story. The US Postal Service saw this division grow six percent last year to 3.7 billion packages despite stiff competition from rivals FedEx and UPS.

Even still, the postal service is losing money hand over fist. According to Reuters, the postal service lost $2 billion during the second quarter compared to a net loss of $740 million during the year-ago period.