A system that allows a user of a first domain to access a second domain. A request originates in the first domain to perform an action in the second domain. The request indicates a user of the first domain on whose behalf the request was originated. The access request is received by an adapter in the second domain. The adapter requests an access token for a user of the second domain who corresponds to the user of the first domain. A mapping table is used to identify which user in the second domain corresponds to the user in the first domain. Once the correct user of the second domain is identified, an access token for that user is returned to the adapter. The adapter then carries out the requested action by using the access token to impersonate the user of the second domain.