USPS now supports a feature called &quot;street addressing&quot;. Basically, instead of writing &quot;PO Box #&quot; as the address, you may write the actual street address of the same facility followed by your box number, something like &quot;123 Main St #456&quot;. Private mailbox providers also often accept addresses like &quot;123 Main St Apt 456&quot;, where 456 is the number of your mailbox as well.