The document discusses different types of mail handled within a business, including incoming mail, outgoing mail, internal mail, facsimiles, e-mail, and registered or recorded delivery mail. Incoming mail must be opened according to procedures, with urgent mail handled first and private mail left sealed. Outgoing mail is sent from the building by services like postal mail, fax, or email. Internal mail is communication within a company between branches via memos, emails, or documents.