migrate to "export default"

also, set no-use-before-define in linter

src/mailserver.js

@@ -2,44 +2,31 @@ import assert from 'node:assert';
 import BoxError from './boxerror.js';
 import constants from './constants.js';
 import debugModule from 'debug';
-import * as dns from './dns.js';
-import * as docker from './docker.js';
-import * as domains from './domains.js';
+import dns from './dns.js';
+import docker from './docker.js';
+import domains from './domains.js';
 import eventlog from './eventlog.js';
 import fs from 'node:fs';
 import hat from './hat.js';
 import infra from './infra_version.js';
 import Location from './location.js';
 import locks from './locks.js';
-import * as mail from './mail.js';
+import mail from './mail.js';
 import paths from './paths.js';
-import * as platform from './platform.js';
-import * as reverseProxy from './reverseproxy.js';
+import platform from './platform.js';
+import reverseProxy from './reverseproxy.js';
 import safe from 'safetydance';
 import services from './services.js';
-import * as settings from './settings.js';
+import settings from './settings.js';
 import shellModule from './shell.js';
 import tasks from './tasks.js';
-import * as users from './users.js';
+import users from './users.js';
 
 const debug = debugModule('box:mailserver');
 const shell = shellModule('mailserver');
 
 const DEFAULT_MEMORY_LIMIT = 512 * 1024 * 1024;
 
-export {
-    restart,
-    start,
-    onDomainAdded,
-    onDomainRemoved,
-    checkCertificate,
-    getMailAuth,
-    getLocation,
-    startChangeLocation,
-    changeLocation,
-    setLocation,
-    DEFAULT_MEMORY_LIMIT,
-};
 
 async function createMailConfig(mailFqdn) {
     assert.strictEqual(typeof mailFqdn, 'string');
@@ -325,3 +312,16 @@ async function getMailAuth() {
     };
 }
 
+export default {
+    restart,
+    start,
+    onDomainAdded,
+    onDomainRemoved,
+    checkCertificate,
+    getMailAuth,
+    getLocation,
+    startChangeLocation,
+    changeLocation,
+    setLocation,
+    DEFAULT_MEMORY_LIMIT,
+};