What is the difference between letters, memos and emails? How do they each differ in terms of content, purpose, and formality? Letters, memos and emails are all forms of written communication. Letters are traditionally written on paper and sent through the mail, memos are typically written for internal communication within an organization, and emails are sent electronically. Each of these forms of communication has different content, purpose and formality. Letters are usually more formal than memos and emails, and often contain more detailed information. Memos are typically used to communicate within an organization and are usually less formal than letters. Emails are typically used to communicate with people outside the organization and are usually the least formal of the three.