U

unauthenticated user

A messaging user that does not have a recognized account on any Microsoft Exchange server. An unauthenticated user can log on to a server anonymously, but is restricted to accessing only the published public folders and address books. Also referred to as an anonymous user.

uniform resource locator

See URL.

URL

(Uniform Resource Locator) A standardized string used to specify a resource on the Internet, such as an HTML document. The format of a URL is "protocol://server.network.domain/path/resource".