We use openldap as a back end for many things. One of the thing, it can be used for is an address book for outlook. Recently we upgrade to 2.4.16->2.4.20 from 2.(who knows how old). Outlook 2003 clients stopped working: http://support.microsoft.com/kb/555536 So I followed the instructions here to enable server side sorting: http://bacedifo.blogspot.com/2009/09/server-side-sort-with-openldap2418.html I was able to add the ordering to the sn attribute. attributetype ( 2.5.4.4 NAME ( 'sn' 'surname' )     DESC 'RFC2256: last (family) name(s) for which the entity is known by'     ORDERING caseIgnoreOrderingMatch     SUP name ) Unfortunately outlook is looking at the cn attribute @400000004b21316a0e808064 sssvlv: no ordering rule specified and no default ordering rule for attribute cn @400000004b21316a0e808834 <= get_ctrls: n=1 rc=18 err="serverSort control: No ordering rule" That unfortunately is not defined in the core.schema # system schema #attributetype ( 2.5.4.3 NAME ( 'cn' 'commonName' ) #       DESC 'RFC2256: common name(s) for which the entity is known by' #       SUP name ) I am sure there is a good reason why cn does not have an ordering, but I am guessing it used to have this in the distant past since this previously worked. So how would I go about changing the system schema? Or does anyone have a better way to deal with this. (I know I could play with client registry (kb) article but I would like to handle this server side) Thank you for your insights.