phpldapadmin faile to create courier email account

Hi,

I integrated the following programs in freebsd 5.4.
phpldapadmin
openldap 2.2_26
courier-imap
courier-authlib
courier-authdaemon
cyrus-sasl2-saslauthd
postfix

When I tried to add new email account to courier-imap, I got the following error shown in the log file:
slapd[1141]: conn=225 fd=10 ACCEPT from IP=10.8.254.251:65479 (IP=0.0.0.0:389)
slapd[1141]: conn=225 op=0 BIND dn="cn=sam,dc=authtec,dc=com" method=128
slapd[1141]: conn=225 op=0 BIND dn="cn=sam,dc=authtec,dc=com" mech=SIMPLE ssf=0
slapd[1141]: conn=225 op=0 RESULT tag=97 err=0 text=
slapd[1141]: conn=225 op=1 ADD dn="uid=wilson.long,dc=authtec,dc=com"
slapd[1141]: conn=225 op=1 RESULT tag=105 err=21 text=objectClass: value #1 invalid per syntax
slapd[1141]: conn=225 op=2 UNBIND
slapd[1141]: conn=225 fd=10 closed

The exact steps I used to create this courier-imap account thru phpldapadmin is:
Click the slapd[1141]: conn=225 fd=10 ACCEPT from IP=10.8.254.251:65479 (IP=0.0.0.0:389)
May 31 23:13:18 mail02 slapd[1141]: conn=225 op=0 BIND dn="cn=sam,dc=authtec,dc=com" method=128
May 31 23:13:18 mail02 slapd[1141]: conn=225 op=0 BIND dn="cn=sam,dc=authtec,dc=com" mech=SIMPLE ssf=0
May 31 23:13:18 mail02 slapd[1141]: conn=225 op=0 RESULT tag=97 err=0 text=
May 31 23:13:18 mail02 slapd[1141]: conn=225 op=1 ADD dn="uid=wilson.wun,dc=authtec,dc=com"
May 31 23:13:18 mail02 slapd[1141]: conn=225 op=1 RESULT tag=105 err=21 text=objectClass: value #1 invalid per syntax
May 31 23:13:19 mail02 slapd[1141]: conn=225 op=2 UNBIND
May 31 23:13:19 mail02 slapd[1141]: conn=225 fd=10 closed

The exact steps I used to create new email account are:
Select option "Create new entry here" in the My LDAP Server page.
Select Courier Mail Account in the Create Object page.
Press the Proceed button.
Fill in the following info:
 uid: wilson.long
 Home directory: /usr/localvmail
 Mailbox: <empty>
 Email: wilson.long@xxxxxxxxxxx
 Password: 123
 Password: 123
 Encryption: clear
 Container: dc=authtec,dc=com
Press the Proceed button.
And press the Create Addres button.

Then the error page shown up:
 Could not add the object to the LDAP server.
 LDAP said: Invalid syntax
 Error number: 0x15 (LDAP_INVALID_SYNTAX)
 Description: An invalid attribute value was specified.

In the above attributes, I don't know hwat is Mailbox I should enter. I use Maildir not Mailbox. How can I change Mailbox to Maildir in phpldapadmin?

Thanks
Sam
.