ERROR: Protocol error
Upgrade to SquirrelMail 1.4.3 and set protocol version to 3 in LDAP address book configuration. If you get this error in other SquirrelMail plugins that use LDAP, ask plugin developers to implement v3 bind protocol options or see other solutions.
The OpenLDAP Quick Start Guide instructions at http://www.openldap.org involve starting and stopping slapd at the command line.
On FreeBSD 4.9, PHP 4.3.4, SquirrelMail 1.4.2, OpenLDAP 2.1.23 there are three requirements to not get this Protocol error
Check that allow bind_v2 was added to /usr/local/etc/openldap/slapd.conf
Check that /etc/rc.conf contains the following entries as mentioned in the ports message after compile of OpenLDAP.\n
slapd_flags='-h "ldapi://%2fvar%2frun%2fopenldap%2fldapi/ ldap://0.0.0.0:389"'
Use /usr/local/etc/rc.d/slapd.sh start to start the slapd daemon and /usr/local/etc/rc.d/slapd.sh stop to stop the daemon
Make sure you stop and start the daemon after you make the configuration changes.
OS X 10.4.X Server
Pico or VI /etc/openldap/slapd_macosxserver.conf
ADD to the file:\nÿ2ÿ
Save & Exit
Restart Slapd w/ the Activity Viewer application or command line\n
N (LDAP Addressbook Number) [enter]
Leave the rest of the settings default except the following:\n
hostname: (Your server hostname)
Protocol Name: Staff (or whatever you want to call it)