feat(storage): add comprehensive tests for StorageManager with memory, filesystem, and custom function backends

feat(email): implement EmailSendJob class for robust email delivery with retry logic and MX record resolution

feat(mail): restructure mail module exports for simplified access to core and delivery functionalities

ts/mail/delivery/smtpserver/data-handler.ts

@@ -4,6 +4,8 @@
  */
 
 import * as plugins from '../../../plugins.ts';
+import * as fs from 'fs';
+import * as path from 'path';
 import { SmtpState } from './interfaces.ts';
 import type { ISmtpSession, ISmtpTransactionResult } from './interfaces.ts';
 import type { IDataHandler, ISmtpServer } from './interfaces.ts';