I thought that the hassle for US based sellers was going to the post office to post international parcels BUT if I'm reading this correctly provided you use one of the computerised tools (Click-N-Ship service, an authorized PC Postage vendor, or the USPS Web Tools system) to print the forms as would seem to be the case on many packages I get from the US you don't have to lodge Priority Mail International or First Class mail at a post office (I didn't check other mail types).
According to those links on the USPS site you can lodge suitable mail, provided postage is paid by a means other than the use of postage stamps:
- In a private mailbox bearing a return address that matches the address at the point of pick up, when the customer or business is known to reside or do business at that location.
- Through Pickup on Demand service.
- Through Package Pickup service.
- At a Postal Service retail counter.
- Into a Postal Service lobby drop.
- In a collection box.
- At a Contract Postal Unit (CPU).
- At a USPS Approved Shipper location.
This might help members in the US