Under ISO 27002 clause 5.12 an organisation labels information according to its value and audience. “Internal” (sometimes “Internal Use Only”) is applied to data meant for distribution to all employees but not outside the organisation. A CEO’s e-mail setting out company status, vision and strategy is intended for the workforce and contains no highly sensitive trade-secret detail that must be limited to a subset of staff. Therefore the appropriate classification is “Internal Mail”.

B. Public Mail – For information intended for external/public release; the message is not authorised for outside audiences.

C. Confidential Mail – Used when access must be limited to specific groups; this message is addressed to the entire staff.

D. Restricted Mail – Highest sensitivity (trade secrets, regulated data); content here is not that critical nor restricted to select personnel.

1. ISO/IEC 27002:2022, clause 5.12 “Information classification” – defines assigning labels such as Internal to material for general staff use.

2. University of Cambridge Information Classification Policy v3.1 (2023) §3, Table 1: “Internal – Internal announcements, newsletters, staff communications”.

3. MIT Information Protection & Handling Standard (MIT IS&T, 2022) §2.3: “Internal Use Only – organisational communications for all employees; not public”.