Use OpenLDAP as address book in Microsoft Outlook

Tested with Outlook 2007:

on account settings choose address book tabs
click new
choose Internet directory service(LDAP)
insert the servername (for me, i set it to IP of the server)
checked this " this server requires me to logon"
Fill the username with --> mail=www@testserver.com,ou=Users,domainName=testserver.com,o=domains,dc=testserver,dc=com, dont forget to insert user passwd
Click "More Settings"
Leave by default,
Click "Search"
Choose "custom" and insert with --> ou=Users,domainName=testserver.com,o=domains,dc=testserver,dc=com
Finish

you need make sure network port 389 (OpenLDAP service) is open on your iRedMail server, otherwise, you need config the iptables.