I had this working with ZCS 5.0.7, but I can't seem to get it working in 6.0.10.

Here's what I've tried, in Thunderbird:

hostname: name.of.zimbra.server
base dn: ou=people,dc=_domainname_,dc=com
scope: subtree
search filter: (mail=*)
Login method: simple

When I search, it appears to succeed but returns 0 results. If I alter the base dn, Thunderbird reports that the replication failed.

Any ideas on how to debug / fix this?