"empty" LDAP addressbooks

Bernhard R. Link blogs about LDAP addressbooks in Thunderb^WIcedove, and mentions:

Also don't be confused by no records shown in the new addressbook. I guess that is some measure against always loading a possibly large remote addressbook. To test just enter anything in the search field, and the matching records should show up nicely. (I'm not sure if all versions allow searching for substrings. If they do, try searching for the at sign, to get a full list.)

Actually, the reason is that an LDAP server is not a database, and it is not required to return the full list of matching items of a search, if that list is sufficiently large (I believe the RFC suggests a minimum of 100 items to be returned); this is to avoid people DoSsing the LDAP server by accident. It also means that the suggestion to search for the at sign to get all items in the directory may not work.