Backported r5392 to release branch

config/main.inc.php.dist

@@ -586,6 +586,7 @@ $rcmail_config['ldap_public']['Verisign'] = array(
   'numsub_filter' => '(objectClass=organizationalUnit)',   // with VLV, we also use numSubOrdinates to query the total number of records. Set this filter to get all numSubOrdinates attributes for counting
   'sizelimit'     => '0',     // Enables you to limit the count of entries fetched. Setting this to 0 means no limit.
   'timelimit'     => '0',     // Sets the number of seconds how long is spend on the search. Setting this to 0 means no limit.
+  'referrals'     => true|false,  // Sets the LDAP_OPT_REFERRALS option. Mostly used in multi-domain Active Directory setups
 
   // definition for contact groups (uncomment if no groups are supported)
   // for the groups base_dn, the user replacements %fu, %u, $d and %dc work as for base_dn (see above)

program/include/rcube_ldap.php

@@ -181,6 +181,9 @@ class rcube_ldap extends rcube_addressbook
                 ldap_set_option($lc, LDAP_OPT_PROTOCOL_VERSION, $this->prop['ldap_version']);
                 $this->prop['host'] = $host;
                 $this->conn = $lc;
+
+                if (isset($this->prop['referrals']))
+                    ldap_set_option($lc, LDAP_OPT_REFERRALS, $this->prop['referrals']);
                 break;
             }
             $this->_debug("S: NOT OK");