[mothered]

I'm ordering a package that will probably fit in that mailbox, and I'm wondering—will they leave it there or by the front door? I could request for USPS to leave it at the door

As far as I'm aware, UPS delivers (In your case) to the residential address.

In some localities and depending on the circumstances, UPS may deliver to the local post office and the Item Is then delivered (from the post office) to the mailbox.