ContactItem.MailingAddressPostOfficeBox Property (Outlook)
Returns or sets a String representing the post office box number portion of the selected mailing address of the contact. Read/write.
This property replicates the property indicated by the SelectedMailingAddress property, which is one of the following OlMailingAddress constants: olBusiness, olHome, olNone, or olOther. While it can be changed or entered independently, any such changes or entries to this property will be overwritten by any subsequent changes or entries to the property indicated by SelectedMailingAddress.