Created attachment 855 [details]
Visual description of problem
If the administrator wants to require group membership in Domain Users@lab.lkpg.cendio.se to log in to ThinLinc, they could add the group name to /vsmserver/allowed_groups configuration via Web Administration. If they did add domain email@example.com via Web Administration, they would end up allowing two groups - domain and firstname.lastname@example.org instead however.
This is *not* what the administrator intended.
This bug does have quite a bit of overlap with bug 2534 but could be solved separately by, for instance, refusing to handle group names with spaces in them.
Found when testing bug 5968 on a i386 Debian 9 system.