What service runs on a Client Access server and returns the correct OAB URL for a specific client connection?

The Autodiscover service is essential for facilitating client configuration settings, including returning the correct Offline Address Book (OAB) URL for clients connecting to the Exchange environment. When a client, such as Microsoft Outlook, attempts to connect, it queries the Autodiscover service to retrieve relevant information needed for its operation, including where to find the OAB.

The Autodiscover service streamlines the process of configuration by automatically providing client devices with the necessary settings. This allows for a seamless experience as users connect to Exchange services without needing to manually configure settings such as URLs for OAB downloads.

In contrast, the CAS service and Exchange services encompass broader functionalities that support client access but do not specifically focus on returning the OAB URL. Outlook Web Access is an interface for accessing email through a web browser and does not function in the same way as Autodiscover regarding OAB URL management. The specificity of Autodiscover in providing such critical information makes it the correct answer in this context.