Postfix: Masquerading_Domains does not work

Dear all!

We are using a SLES 10 SP2 system where we installed a
Mail Server according to this tutorial:

Cool Solutions: Configuring a Mail Server on SLES

Everything is running fine except for the Masquerading
feature. For instance the e-mail sender should have this
"user@example.com" form but it appears as "user@mail-s.
example.com".
Here is now the relevant /etc/postfix/main.cf entry:
...............
...............
masquerade_domains=ldap:/etc/postfix/ldapmasquerade_
domains.cf
.................

ldapmasquerade_domains.cf has this content:
# This file was created by yast2-mail-server. Please do
not edit it!
server_host=localhost
query_filter=(&(objectclass=suseMailDomain)(zoneName=%s)
(suseMailDomainMasquerading=yes))
search_base=ou=DNS,dc=example,dc=com
timeout=20
result_attribute=zoneName
bind=no
server_port=389
scope=sub
#

By using "masquerade_domains=example.com" in the main.cf
file, the sender is now as we want to see it ie.
"user@example.com".

Any idea what's wrong with the ldapmasquerade_domains.cf
configuration?

THX, Rainer