I finally setup LDAP on Kerio. I now have my contacts synced with webmail, mac address book and my phone. Awesome.
Anyone who uses our email server can now make use of this too.
The server (mail.lttd.net) allows secure LDAP connections on port 16360 (636 is the standard port but the mail server is also a domain controller, so that port is in use).
More details can be found in the Kerio User Manual:http://download.kerio.com/dwn/kmsug6-en.pdf