I in the LDAP section of your client application there should be a section for adding a host to lookup an LDAP etc.
I'm not sure if this is what your talking about, however, for example with Kontact I just go to konfigure knotact and add a LDAP host, which is the domain name of my sme server, then scan for host and it finds it automatically, then search all and it finds all the contacts in the sme / horde mail service.
I basically just added domain.com to my host list for my kontact manager and boom it worked, I did not actually have to mention Horde, I simply used the domain name.
I'm not exactly sure if this is what you were attempting to achieve but I hope it's helpful.