--- a/src/mail/ngx_mail_core_module.c
+++ b/src/mail/ngx_mail_core_module.c
@@ -154,13 +154,14 @@ ngx_mail_core_create_srv_conf(ngx_conf_t
      * set by ngx_pcalloc():
      *
      *     cscf->protocol = NULL;
-     *     cscf->resolver = NULL;
      */
 
     cscf->timeout = NGX_CONF_UNSET_MSEC;
     cscf->resolver_timeout = NGX_CONF_UNSET_MSEC;
     cscf->so_keepalive = NGX_CONF_UNSET;
 
+    cscf->resolver = NGX_CONF_UNSET_PTR;
+
     cscf->file_name = cf->conf_file->file.name.data;
     cscf->line = cf->conf_file->line;
 
@@ -207,9 +208,7 @@ ngx_mail_core_merge_srv_conf(ngx_conf_t 
         return NGX_CONF_ERROR;
     }
 
-    if (conf->resolver == NULL) {
-        conf->resolver = prev->resolver;
-    }
+    ngx_conf_merge_ptr_value(conf->resolver, prev->resolver, NULL);
 
     return NGX_CONF_OK;
 }
@@ -423,6 +422,11 @@ ngx_mail_core_resolver(ngx_conf_t *cf, n
 
     value = cf->args->elts;
 
+    if (ngx_strcmp(value[1].data, "off") == 0) {
+        cscf->resolver = NULL;
+        return NGX_CONF_OK;
+    }
+
     ngx_memzero(&u, sizeof(ngx_url_t));
 
     u.host = value[1];
@@ -435,7 +439,7 @@ ngx_mail_core_resolver(ngx_conf_t *cf, n
 
     cscf->resolver = ngx_resolver_create(&u.addrs[0], cf->cycle->new_log);
     if (cscf->resolver == NULL) {
-        return NGX_OK;
+        return NGX_CONF_OK;
     }
 
     return NGX_CONF_OK;