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Hello List

I am trying to use sympa with LDAP lookups, but every time I try to log in to 
the webinterface i get rejected

I am using sympa version 3.3.3 and this is what my auth.conf looks like:

ldap
        host                            127.0.0.1:389
        timeout                         0
        bind_dn                         uid=vmail,dc=system-users,dc=dot
        bind_password                   XXXXXX
        suffix                          dc=dot
        get_dn_by_uid_filter            (uid=[sender])
        get_dn_by_email_filter          (|(mail=[sender])(maildrop=[sender]))
        email_attribute                 mail
        alternative_email_attribute     maildrop
        scope                           sub

I tried logging in both with an email adress and a uid to no avail.
I have checked the debugging output of my LDAP logs and found the following 
bind operation as soon as i try to log into the webinterface (an example 
where I tried using just an ldap uid):

Jan  6 12:14:06 disc slapd[8544]: conn=334 fd=15 ACCEPT from 
IP=127.0.0.1:39598 (IP=0.0.0.0:389) 
Jan  6 12:14:06 disc slapd[8559]: conn=334 op=0 BIND dn="" method=128 
Jan  6 12:14:06 disc slapd[8559]: conn=334 op=0 RESULT tag=97 err=0 text= 
Jan  6 12:14:06 disc slapd[8544]: deferring operation 
Jan  6 12:14:06 disc slapd[8610]: conn=334 op=1 SRCH base="dc=dot" scope=2
filter="(uid=dec)" 
Jan  6 12:14:06 disc slapd[8610]: => access_allowed: search access to 
"uid=dec,ou=users,dc=dec,dc=org,dc=dot" "uid" requested 

<some acl matching deleted for brevity>

Jan  6 12:14:06 disc slapd[8610]: => acl_mask: to value by "", (=n)  
Jan  6 12:14:06 disc slapd[8610]: => access_allowed: search access denied by 
=n 

Can anybody tell me why the bind occurs without any dn (conn=334 op=0 BIND 
dn="" method=128) even though I have supplied one in the auth.conf?

Thank's in advance for any help.