Postfix LDAP% s is not resolved in email

I am using tvial / dockerserver (which may not be related to the problem) and I configure an file like this

bind              = yes
bind_dn           = {{ ldap_readonly_user }}
bind_pw           = {{ ldap_readonly_password }}
query_filter      = (&(objectClass=mailAlias)(mailalias=%s))
result_attribute  = mail
search_base       = ou=Mail,{{ main_suffix }}
server_host       = {{ mail_ldap_server }}
start_tls         = no
version           = 3

with that, I see that postfix is ​​resolving as

5e2d2eda conn=15023 op=2 SRCH base="ou=Mail,dc=XXX,dc=XX" scope=2 deref=0 filter="(&(objectClass=mailAlias)("

I would expect to resolve as


When I do it

$ postmap -q ldap:/etc/postfix/

(which is exactly what I want).

According to the postfix documentation% s should work. Replacing it with "% u @% d" does not generate any query.
How to debug / solve this?