What type of correspondence must not be opened without the addressee's permission?

Personal correspondence must not be opened without the addressee's permission because it is considered private and confidential. This type of mail is addressed to an individual and typically contains personal information or communications that the sender intends only for the recipient to read. Opening such correspondence without consent would violate the sender's privacy rights and potentially lead to legal repercussions or disciplinary action within the department.

In contrast, other categories of correspondence like official division communications or inter-departmental mail may have different protocols that allow for oversight in the interests of the department or organization. General correspondence also does not carry the same expectation of privacy as personal correspondence, which emphasizes the necessity of respecting the confidentiality surrounding individual communications. The distinction lies primarily in the privacy rights associated with personal information, underscoring the importance of consent in handling such correspondence.