PMBOK identifies communication dimensions including internal vs. external and formal vs. informal. “Formal” examples explicitly include reports and minutes, aligning formal communications with reports, agendas, and minutes. “Informal” examples include emails, matching “general communications activities using email.” “Internal” is communication within the project (i.e., project stakeholders), while “External” targets customers and vendors.

PMI further describes internal communications as directed to project team members and external communications as directed to stakeholders not on the team (customers, regulators, vendors), reinforcing the mapping.

PMI, A Guide to the Project Management Body of Knowledge (PMBOK® Guide), Fifth Edition, Section 10 “Project Communications Management,” pp. 312–313: lists dimensions (internal/external; formal/informal) with examples: reports, minutes (formal) and emails (informal).

ceulearning.ceu.edu

PMI Learning Library, Matassa, P. (2007). “Bringing your project communications into the 21st century,” defines internal communications (to project team members) and external communications (to non-team stakeholders such as customers), clarifying audiences for each dimension.