Ive yet to come across a great description of what LDAP is and does. From my understanding it acts as a frontend for a database like MySQL. My ultimate goal is to get Mozilla Thunderbird running with database support for an addressbook and calendar so that they are accessible from webmail (Horde) as well as thunderbird. I know thunderbird has LDAP acess built in, but is it what I want? Should i jsut try to find a Thudnerbird extension that allows straight MySQL access? I currently have MySQL5 installed on my Debian Etch server, and I am very happy with its performance. What kind of overhead does LDAP create? Will LDAP create any issues with php or cgi based web apps that access the MySQL database directly? Is there anythign else I should know before trying to install LDAP? Thanks for your help.