diff --git a/lib/api/kolab_api_service_domain.php b/lib/api/kolab_api_service_domain.php
--- a/lib/api/kolab_api_service_domain.php
+++ b/lib/api/kolab_api_service_domain.php
@@ -174,7 +174,7 @@
 
         $attributes = $this->parse_input_attributes('domain', $postdata, $postdata['type_id']);
 
-        $this->_mod_domain_attrs(null, $attributes);
+        $this->_mod_domain_attrs(null, $attributes, $postdata['id']);
 
         $result = $auth->domain_edit($postdata['id'], $attributes, $postdata['type_id']);
 
@@ -278,7 +278,7 @@
     /**
      * Modify hosted domain attributes
      */
-    protected function _mod_domain_attrs($domain, &$attributes)
+    protected function _mod_domain_attrs($domain, &$attributes, $olddn = null)
     {
         // Generate attributes (aci, inetdomainbasedn) for hosted domains
         $conf = Conf::get_instance();
@@ -328,8 +328,31 @@
                 . 'ldap:///cn=kolab-admin,' . $mgmt_root_dn . '");)'
             );
 
-            $attributes['aci']              = $aci;
-            $attributes['inetdomainbasedn'] = $domain_root_dn;
+            // Preserve important old aci and inetdomainbasedn attributes of the
+            // management and hosted domain.
+            if (!empty($olddn)) {
+                $auth = Auth::get_instance();
+                $info = $auth->domain_info($olddn);
+                if (!empty($info)) {
+                    $oldattributes = reset($info);
+                    if (!empty($oldattributes['inetdomainbasedn'])
+                        && $oldattributes['inetdomainbasedn'] == $hosted_root_dn
+                        || "dc=".implode(",dc=",explode(".",$domain)) == $mgmt_root_dn
+                    ) {
+                        $aci = $oldattributes['aci'];
+                        if (!empty($oldattributes['inetdomainbasedn'])) {
+                            $domain_root_dn = $oldattributes['inetdomainbasedn'];
+                        } else {
+                            $domain_root_dn = null;
+                        }
+                    }
+                }
+            }
+
+            $attributes['aci'] = $aci;
+            if (!empty($domain_root_dn)) {
+                $attributes['inetdomainbasedn'] = $domain_root_dn;
+            }
 
             $this->is_hosted = true;
         }