A private mail bag (PMB), locked bag or caller service is a term for a special form of postal delivery in some countries, usually a government department or large private company, which receive large volumes of mail.
Private mail bag addresses are often used in countries in Africa where there may be no street delivery service.
Like PO Box addresses, private mail bag addresses omit the name of the building and street, and include only the number allocated to the user.
In other countries, particularly South Africa, New Zealand and Fiji, the term private bag is used.
In Fiji the usage is similar to New Zealand In South Africa, the private bag number may also contain letters.