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

test/suite/smtpclient_rfc-compliance/test.crfc-04.response-codes.ts

@@ -0,0 +1,54 @@
+import { expect, tap } from '@git.zone/tstest/tapbundle';
+import { createTestServer } from '../../helpers/server.loader.ts';
+import { createTestSmtpClient } from '../../helpers/smtp.client.ts';
+import { Email } from '../../../ts/mail/core/classes.email.ts';
+
+tap.test('CRFC-04: SMTP Response Code Handling', async () => {
+  console.log('\n📧 Testing SMTP Client Response Code Handling');
+  console.log('=' .repeat(60));
+
+  const testServer = await createTestServer({});
+
+  try {
+    const smtpClient = createTestSmtpClient({
+      host: testServer.hostname,
+      port: testServer.port
+    });
+
+    console.log('\nTest 1: Successful email (2xx responses)');
+    const email1 = new Email({
+      from: 'sender@example.com',
+      to: ['recipient@example.com'],
+      subject: 'Success test',
+      text: 'Testing successful response codes'
+    });
+
+    const result1 = await smtpClient.sendMail(email1);
+    console.log('  ✓ 2xx response codes handled correctly');
+    expect(result1).toBeDefined();
+
+    console.log('\nTest 2: Verify connection');
+    const verified = await smtpClient.verify();
+    console.log('  ✓ Connection verification successful');
+    expect(verified).toBeDefined();
+
+    console.log('\nTest 3: Multiple recipients (multiple 250 responses)');
+    const email2 = new Email({
+      from: 'sender@example.com',
+      to: ['user1@example.com', 'user2@example.com', 'user3@example.com'],
+      subject: 'Multiple recipients',
+      text: 'Testing multiple positive responses'
+    });
+
+    const result2 = await smtpClient.sendMail(email2);
+    console.log('  ✓ Multiple positive responses handled');
+    expect(result2).toBeDefined();
+
+    console.log('\n✅ CRFC-04: Response code handling tests completed');
+
+  } finally {
+    testServer.server.close();
+  }
+});
+
+tap.start();