I live in the chicagoland area and I always got my books from amazon through USPS, however earlier this month amazon started sending stuff through Velocity Express, well the books I order are for an inmate in jail so I was wondering if they ship to P.O. Boxes? I've tried google, and their website and got no information.
But don't confuse a PO Box at the Post Office with a private mailbox (PMB) at a mailbox store. They are different things.
Your PO Box address must be entered correctly for some shipping programs to recognize it as a PO Box.
Your Name PO BOX 12345 Your City, ST 99999
Note that there is no street address associated with the PO Box, and that it specifically says "PO BOX".
Last year, USPS started testing a program in which PO Box holders could get packages from any carrier at their PO Box. This is offered in just very, very select locations, and the address you would use to do so is the street address of the Post Office. (Don't just try this unless you've specifically were offered, and signed-up for this service.) USPS did *not* get permission from the PRC to expand this program beyond the very limited test markets.
So with that exception of the test USPS is doing in limited markets, the law still prohibits receiving packages that do not include "postage" (something the mailer pays to USPS) at a PO Box.
If your package is coming by Velocity Express, your address must not be formatted correctly as a PO Box address, otherwise Amazon's shipping software would choose USPS as the only available option.