I got a user group filter to work in my test environment.
User Filter Examle:
(&(objectCategory=Person)(sAMAccountName=*)(memberOf=CN=Zammad Users,OU=Global Groups,OU=Department,DC=company,DC=dot,DC=com))
When I enable the filter, scheduler gets angry, LDAP sync gets stuck and also indexjob, causing thousands of jobs to fail.
Following @MrGeneration instructions on [solved] 1772421 background jobs in queue fixed all the failing jobs, took all night to finish reindexing.
So due to my poor initial LDAP config (not Zammads fault! although a LDAP query would be better imo than sync) I have close to 500,000 unwanted users…not sure if expert mode was available when we rolled out Zammad a couple years ago…anyways hoping the delete feature comes out soon since we hoped it would have been released at the end of 2018.
Thanks