Similar to email, sometime inter-office memorandums are shared within a department or larger work unit.
Suppose you are a CEO in an organization and you want to inform your department heads about the value of online education and its contributions to internal promotions regarding professional communications. Write a 300 word inter-office memorandum to your department heads discussing why online education is necessary (purpose), expectations, and advice on how to seek online education and/or be successful in an online education program in the field of professional communications.