Which of the following is NOT a function of a mail user agent?

Mail user agents (MUAs) are software applications that enable users to send, receive, and organize their email messages. The primary functions of an MUA include managing personal email accounts and providing user-friendly interfaces for interacting with emails.

Organizing emails allows users to categorize and manage their messages effectively, making it easier to locate important communications. Sending emails involves composing messages and transmitting them to the intended recipients, while receiving emails refers to the ability to access and view incoming messages from a mail server.

Routing emails, however, is not a function performed by the mail user agent itself. Instead, routing is typically handled by mail transfer agents (MTAs) or mail servers, which are responsible for directing emails from the sender to the receiver based on the recipient's address. Therefore, the function of routing emails falls outside the scope of what a mail user agent does, making it the correct answer in this context.