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/routing/classes.unified.email.server.ts

@@ -1,5 +1,6 @@
 import * as plugins from '../../plugins.ts';
 import * as paths from '../../paths.ts';
+import { EventEmitter } from 'events';
 import { logger } from '../../logger.ts';
 import { 
   SecurityLogger, 
@@ -28,7 +29,7 @@ import { UnifiedDeliveryQueue, type IQueueOptions } from '../delivery/classes.de
 import { UnifiedRateLimiter, type IHierarchicalRateLimits } from '../delivery/classes.unified.rate.limiter.ts';
 import { SmtpState } from '../delivery/interfaces.ts';
 import type { EmailProcessingMode, ISmtpSession as IBaseSmtpSession } from '../delivery/interfaces.ts';
-import type { DcRouter } from '../../classes.mailer.ts';
+import type { DcRouter } from '../../classes.dcrouter.ts';
 
 /**
  * Extended SMTP session interface with route information
@@ -153,7 +154,7 @@ export interface IServerStats {
 /**
  * Unified email server that handles all email traffic with pattern-based routing
  */
-export class UnifiedEmailServer extends plugins.EventEmitter {
+export class UnifiedEmailServer extends EventEmitter {
   private dcRouter: DcRouter;
   private options: IUnifiedEmailServerOptions;
   private emailRouter: EmailRouter;