I am trying to use an existing FirstClass 7.1 server as GAL source for Zimbra. Whenever the admin GUI asks me to do a test search I get java exceptions like:
javax.naming.ServiceUnavailableException: mydomain.com:389; socket closed; remaining name 'dc=mydomain,dc=com'
and then a long "java blurp".

I am specially confused by the "socket closed" message as accessing the FirstClass LDAP-server via ldapsearch from the zimbra server works fine.
I played around with various search filters but always get java execptions.

Zimbra version: 4.5.5 on a Debian 3.1 system.

Any ideas?