Hi, Jens: actually, my rootdn was " cn=root,dc=koal,dc=com" in both my vldap.h and slapd.conf in the before, and i ensured that the basedn in vldap.h was "ou=people,dc=koal,dc=com" . i tested what you mentioned just now, this cann't help me . the "err acck ,child crashed " error remains. if i input a user which doesn't exsit, it will reports " err authorization failed". if i input the correct user and password, it will reports" err acck, child crashed" . i think it has recognized the user and password ,but sth lead to the "child crashed" error. i have searched the vpopmail mailing list, there were many reports about the same error, and it seems that many reasons will lead to this error, but until now, i still havn't find any valuable solution to me. my configure parameters: ./configure --enalbe-ldap=y --enable-roaming-users=y --enable-logging=y redhat 7.3 vpopmail-5.3.20 openldap-2.0.27 qmailadmin-1.0.20 any suggestions? thanks a lot, :-),