The US Postal Service lets companies give people or offices a private mailbox, or PMB, address to make it easier to send mail within the company. This is a service that people and businesses can get from commercial mail receiving agencies (CMRAs) like UPS. Personal mailboxes are another name for PMBs.
PMB addresses let small businesses have a professional-looking street address, have someone there to sign for letters or packages during regular delivery hours, pick up mail at convenient times, and keep their privacy, which can be important for people who run businesses out of their homes. A CMRA can be used to rent a PMB address when needed. This may be cheaper than renting a box at the post office.