Messaging Server (sharing folder) searching LDAP is not indexed, why?

Question

There's an feature of "sharing a mail folder"
in JMS (Java Messaging Server), whereby
a user could share a folder with another user.
But when a user (uid) is entered into
the "Admission List" box, and the Add button
is pressed, it failed with some error messages
Invalid user and Admin Limit exceeded.
I've asked in the JMS forum and Shane said
this:
The "Administrative limit exceeded" error agrees with the Notes=U and etime=12 in the LDAP access log file. The problem is that the search is not indexed and therefore taking long enough to run foul of the timelimit. You will need to consult with Directory Server experts to determine why this search is not indexed and resolve that.
Could someone enlighten me on what I've
missed out when I've configured the Ldap
server during my installation of the JES system

Answer 1

Here are the extracts of the access and error logs when the "Add" button (after a uid was entered into the box) was clicked.
Invalid user error line appeared on screen
Error log:
WARNING<20805> - Backend Database - search is not indexed base='o=bunet' filter='(&(&(mailUserStatus=active)(objectClass=inetmailuser)(mailHost=jsms.our.domain)(uid=cmtsang))(!(mgmanHidden=true)))' scope='sub'
Access log:
SRCH base="o=bunet" scope=2
filter="(&(&(mailUserStatus=active)(objectClass=inetmailuser)
(mailHost=netnet.our.top.domain)(uid=cmtsang))(!(mgmanHidden=true)))" attrs="cn mail sn telephoneNumber department"
RESULT err=0 tag=101 nentries=1 etime=7 notes=U