Try enabling SSSD

dovecot.nix

@@ -207,6 +207,48 @@ in {
           after = [ "dovecot2.service" ];
         };
 
+        sssd = {
+          enable = true;
+          environmentFile = "/run/dovecotSecrets/sssd.env";
+          config = ''
+            [nss]
+            filter_users = root
+            filter_groups = root
+            reconnection_retries = 3
+
+            [sssd]
+            config_file_version = 2
+            reconnection_retries = 3
+            sbus_timeout = 30
+            domains = informis.land
+            services = nss, pam
+
+            [pam]
+            reconnection_retries = 3
+
+            [domain/informis.land]
+            cache_credentials = False
+            id_provider = ldap
+            auth_provider = ldap
+            access_provider = ldap
+            chpass_provider = ldap
+            ldap_uri = SSSD_LDAP_SERVER
+
+            ldap_schema = rfc2307bis
+            ldap_search_base = SSSD_LDAP_SEARCH_BASE
+            ldap_user_search_base = SSSD_LDAP_USER_SEARCH_BASE
+            ldap_group_search_base = SSSD_LDAP_GROUP_SEARCH_BASE
+
+            ldap_user_object_class = user
+            ldap_user_name = cn
+            ldap_group_object_class = group
+            ldap_group_name = cn
+
+            ldap_default_bind_fn = SSSD_LDAP_BIND_DN
+            ldap_default_authtok = SSSD_LDAP_AUTH_TOKEN
+          '';
+        };
+
         dovecot-sieve-generator = let
           isRegularFile = _: type: type == "regular";
           sieves = filterAttrs isRegularFile (builtins.readDir ./sieves);
@@ -356,7 +398,6 @@ in {
 
           passdb {
             driver = ldap
-            user_format = %n
             args = ${cfg.ldap-conf}
           }