Which channel is considered important for external communication?

Letters are considered an important channel for external communication because they provide a formal method of conveying information to individuals outside of an organization. This form of communication is often used in professional settings to establish a record of correspondence, provide official notices, or respond to inquiries. Letters tend to have a more professional tone and format, making them suitable for communicating with clients, vendors, stakeholders, or other external parties.

In contrast, while text messages, memos, and instant messaging can be useful for internal communication or casual exchanges, they may not carry the same level of formality or appropriate context required for external interactions. Therefore, letters stand out due to their ability to convey professionalism and establish a formal relationship with an external audience.