MR -https://gitlab.cloudforms.lab.eng.rdu2.redhat.com/cloudforms/cfme/merge_requests/924
Verified that the user resolution using both name and name@domain works in 5.5.5.2 I user the username and it correctly found out the user in AD. The created user in the Access Control has name@domain in there. Then I tried it again with the name@domain and it worked too.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://rhn.redhat.com/errata/RHBA-2016-1488.html