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_security/test.csec-08.authentication-fallback.ts

@@ -0,0 +1,154 @@
+import { tap, expect } from '@git.zone/tstest/tapbundle';
+import { startTestServer, stopTestServer, type ITestServer } from '../../helpers/server.loader.ts';
+import { createTestSmtpClient } from '../../helpers/smtp.client.ts';
+import { Email } from '../../../ts/mail/core/classes.email.ts';
+
+let testServer: ITestServer;
+
+tap.test('setup test SMTP server', async () => {
+  testServer = await startTestServer({
+    port: 2568,
+    tlsEnabled: false,
+    authRequired: true
+  });
+  expect(testServer).toBeTruthy();
+  expect(testServer.port).toBeGreaterThan(0);
+});
+
+tap.test('CSEC-08: Multiple authentication methods', async () => {
+  const smtpClient = createTestSmtpClient({
+    host: testServer.hostname,
+    port: testServer.port,
+    secure: false,
+    auth: {
+      user: 'testuser',
+      pass: 'testpass'
+    }
+  });
+
+  const email = new Email({
+    from: 'sender@example.com',
+    to: ['recipient@example.com'],
+    subject: 'Multi-auth test',
+    text: 'Testing multiple authentication methods'
+  });
+
+  const result = await smtpClient.sendMail(email);
+  console.log('Authentication successful');
+  expect(result.success).toBeTruthy();
+
+  await smtpClient.close();
+});
+
+tap.test('CSEC-08: OAuth2 fallback to password auth', async () => {
+  // Test with OAuth2 token (will fail and fallback)
+  const oauthClient = createTestSmtpClient({
+    host: testServer.hostname,
+    port: testServer.port,
+    secure: false,
+    auth: {
+      oauth2: {
+        user: 'user@example.com',
+        clientId: 'test-client',
+        clientSecret: 'test-secret',
+        refreshToken: 'refresh-token',
+        accessToken: 'invalid-token'
+      }
+    }
+  });
+
+  const email = new Email({
+    from: 'sender@example.com',
+    to: ['recipient@example.com'],
+    subject: 'OAuth2 fallback test',
+    text: 'Testing OAuth2 authentication fallback'
+  });
+
+  try {
+    await oauthClient.sendMail(email);
+    console.log('OAuth2 authentication attempted');
+  } catch (error) {
+    console.log(`OAuth2 failed as expected: ${error.message}`);
+  }
+
+  await oauthClient.close();
+
+  // Test fallback to password auth
+  const fallbackClient = createTestSmtpClient({
+    host: testServer.hostname,
+    port: testServer.port,
+    secure: false,
+    auth: {
+      user: 'testuser',
+      pass: 'testpass'
+    }
+  });
+  
+  const result = await fallbackClient.sendMail(email);
+  console.log('Fallback authentication successful');
+  expect(result.success).toBeTruthy();
+
+  await fallbackClient.close();
+});
+
+tap.test('CSEC-08: Auth method preference', async () => {
+  // Test with specific auth method preference
+  const smtpClient = createTestSmtpClient({
+    host: testServer.hostname,
+    port: testServer.port,
+    secure: false,
+    auth: {
+      user: 'testuser',
+      pass: 'testpass',
+      method: 'PLAIN'  // Prefer PLAIN auth
+    }
+  });
+
+  const email = new Email({
+    from: 'sender@example.com',
+    to: ['recipient@example.com'],
+    subject: 'Auth preference test',
+    text: 'Testing authentication method preference'
+  });
+
+  const result = await smtpClient.sendMail(email);
+  console.log('Authentication with preferred method successful');
+  expect(result.success).toBeTruthy();
+
+  await smtpClient.close();
+});
+
+tap.test('CSEC-08: Secure auth requirements', async () => {
+  // Test authentication behavior with security requirements
+  const smtpClient = createTestSmtpClient({
+    host: testServer.hostname,
+    port: testServer.port,
+    secure: false,
+    auth: {
+      user: 'testuser',
+      pass: 'testpass'
+    },
+    requireTLS: false  // Allow auth over plain connection for test
+  });
+
+  const email = new Email({
+    from: 'sender@example.com',
+    to: ['recipient@example.com'],
+    subject: 'Secure auth test',
+    text: 'Testing secure authentication requirements'
+  });
+
+  const result = await smtpClient.sendMail(email);
+  console.log('Authentication completed');
+  expect(result.success).toBeTruthy();
+
+  await smtpClient.close();
+});
+
+tap.test('cleanup test SMTP server', async () => {
+  if (testServer) {
+    await stopTestServer(testServer);
+  }
+});
+
+tap.start();