[Exim] alias query

We are moving to a LDAP base config.
Before we had an alias file entry

all:    tcurdt,someoneelse,anotherone,wholestaff

How can this be achieved with an
LDAP query? I tried:

virtual_all:
  driver = aliasfile
  search_type = ldap
  # get all uids
  query = "ldap:///dc=dff,dc=local?uid?sub?\
           (&(objectclass=POSIXACCOUNT)(uid=*))"
  file_transport = address_file
  pipe_transport = address_pipe

But this yields:

# sendmail -bt all@???
all@??? cannot be resolved at this time:
search_find deferred: LDAP search: too many (20) results (filter not
specific enough)

Looks like the query is more of a boolean
condition that fails or succeeds with 1 result.

But in the manual it says:
|Other forms of alias file (DBM),NIS,etc.) involve
|lookups using the local part as a key on files
|and databases. The value returned is a list of
|address, file, or pipe items separeted by
|commas or newlines.
--
Torsten