Which component is necessary for setting up an Email Threading View?

The component essential for establishing an Email Threading View is the Email Thread Group. This group organizes email messages based on their relationships, such as replies, forwards, or original messages. The Email Thread Group enables users to visualize the connections between emails, simplifying the analysis of communication patterns and ensuring that all relevant information from a threaded discussion is readily accessible.

While other elements like Textual Near Duplicate Group or Control Number may play important roles in different contexts, they are not specifically designed for setting up the threading of emails. The Email Thread Group is uniquely focused on handling email correspondence and displaying it in an organized thread format, making it the correct answer.