What does the Transport service in Exchange Server do?

The Transport service in Exchange Server primarily focuses on the movement of email messages across the messaging architecture, ensuring that each message is efficiently routed and delivered to its intended destination. This includes handling the SMTP protocol, managing routing decisions based on cost and availability, and facilitating communication between different servers in an Exchange organization as well as with external mail systems.

By managing the transport of email, this service ensures that messages are transmitted correctly and quickly, allowing for reliable communication among users. The core functions of the Transport service make it critical for the overall operation of email delivery within Exchange, which is why this answer correctly identifies its primary responsibility.