A user composes messages, and later reads the replies, in a program running on their own laptop. Which component of the Internet mail architecture is that program?
A user composes messages, and later reads the replies, in a program running on their own laptop. Which component of the Internet mail architecture is that program?
Answer
Message User Agent
Options - A. Message User Agent - B. Message Store - C. Mail Submission Agent - D. Message Transfer Agent Why - A. Correct. The MUA acts for the *user*: the author MUA formats and submits, the recipient MUA stores or displays. - B. The MS is where mail sits waiting to be collected. It is storage, not a program acting for the user. - C. The MSA acts for the *hosting domain*, applying its policies at the moment of submission. - D. The MTA relays for one hop and adds trace headers. It acts for the transfer service, not for either user. All four options are real components from the same architecture, so this is pure role recall. The discriminator is always *whose representative is it*: user (MUA), hosting domain (MSA), transfer service (MTA), storage (MS).
Stallings & Brown 5e ch22 §22.1–22.2