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_connection/test.ccm-09.ipv6-dual-stack.ts

@@ -0,0 +1,167 @@
+import { tap, expect } from '@git.zone/tstest/tapbundle';
+import { startTestServer, stopTestServer, type ITestServer } from '../../helpers/server.loader.ts';
+import { createSmtpClient } from '../../../ts/mail/delivery/smtpclient/index.ts';
+import * as net from 'net';
+import * as os from 'os';
+
+let testServer: ITestServer;
+
+tap.test('setup test SMTP server', async () => {
+  testServer = await startTestServer({
+    port: 2535,
+    tlsEnabled: false,
+    authRequired: false
+  });
+  expect(testServer).toBeTruthy();
+  expect(testServer.port).toEqual(2535);
+});
+
+tap.test('CCM-09: Check system IPv6 support', async () => {
+  const networkInterfaces = os.networkInterfaces();
+  let hasIPv6 = false;
+  
+  for (const interfaceName in networkInterfaces) {
+    const interfaces = networkInterfaces[interfaceName];
+    if (interfaces) {
+      for (const iface of interfaces) {
+        if (iface.family === 'IPv6' && !iface.internal) {
+          hasIPv6 = true;
+          console.log(`Found IPv6 address: ${iface.address} on ${interfaceName}`);
+        }
+      }
+    }
+  }
+  
+  console.log(`System has IPv6 support: ${hasIPv6}`);
+});
+
+tap.test('CCM-09: IPv4 connection test', async () => {
+  const smtpClient = createSmtpClient({
+    host: '127.0.0.1', // Explicit IPv4
+    port: testServer.port,
+    secure: false,
+    connectionTimeout: 5000,
+    debug: true
+  });
+
+  // Test connection using verify
+  const verified = await smtpClient.verify();
+  expect(verified).toBeTrue();
+  
+  console.log('Successfully connected via IPv4');
+  
+  await smtpClient.close();
+});
+
+tap.test('CCM-09: IPv6 connection test (if supported)', async () => {
+  // Check if IPv6 is available
+  const hasIPv6 = await new Promise<boolean>((resolve) => {
+    const testSocket = net.createConnection({
+      host: '::1',
+      port: 1, // Any port, will fail but tells us if IPv6 works
+      timeout: 100
+    });
+    
+    testSocket.on('error', (err: any) => {
+      // ECONNREFUSED means IPv6 works but port is closed (expected)
+      // ENETUNREACH or EAFNOSUPPORT means IPv6 not available
+      resolve(err.code === 'ECONNREFUSED');
+    });
+    
+    testSocket.on('connect', () => {
+      testSocket.end();
+      resolve(true);
+    });
+  });
+
+  if (!hasIPv6) {
+    console.log('IPv6 not available on this system, skipping IPv6 tests');
+    return;
+  }
+
+  // Try IPv6 connection
+  const smtpClient = createSmtpClient({
+    host: '::1', // IPv6 loopback
+    port: testServer.port,
+    secure: false,
+    connectionTimeout: 5000,
+    debug: true
+  });
+
+  try {
+    const verified = await smtpClient.verify();
+    if (verified) {
+      console.log('Successfully connected via IPv6');
+      await smtpClient.close();
+    } else {
+      console.log('IPv6 connection failed (server may not support IPv6)');
+    }
+  } catch (error: any) {
+    console.log('IPv6 connection failed (server may not support IPv6):', error.message);
+  }
+});
+
+tap.test('CCM-09: Hostname resolution preference', async () => {
+  // Test that client can handle hostnames that resolve to both IPv4 and IPv6
+  const smtpClient = createSmtpClient({
+    host: 'localhost', // Should resolve to both 127.0.0.1 and ::1
+    port: testServer.port,
+    secure: false,
+    connectionTimeout: 5000,
+    debug: true
+  });
+
+  const verified = await smtpClient.verify();
+  expect(verified).toBeTrue();
+
+  console.log('Successfully connected to localhost');
+
+  await smtpClient.close();
+});
+
+tap.test('CCM-09: Happy Eyeballs algorithm simulation', async () => {
+  // Test connecting to multiple addresses with preference
+  const addresses = ['127.0.0.1', '::1', 'localhost'];
+  const results: Array<{ address: string; time: number; success: boolean }> = [];
+
+  for (const address of addresses) {
+    const startTime = Date.now();
+    const smtpClient = createSmtpClient({
+      host: address,
+      port: testServer.port,
+      secure: false,
+      connectionTimeout: 1000,
+      debug: false
+    });
+
+    try {
+      const verified = await smtpClient.verify();
+      const elapsed = Date.now() - startTime;
+      results.push({ address, time: elapsed, success: verified });
+      
+      if (verified) {
+        await smtpClient.close();
+      }
+    } catch (error) {
+      const elapsed = Date.now() - startTime;
+      results.push({ address, time: elapsed, success: false });
+    }
+  }
+
+  console.log('Connection race results:');
+  results.forEach(r => {
+    console.log(`  ${r.address}: ${r.success ? 'SUCCESS' : 'FAILED'} in ${r.time}ms`);
+  });
+
+  // At least one should succeed
+  const successfulConnections = results.filter(r => r.success);
+  expect(successfulConnections.length).toBeGreaterThan(0);
+});
+
+tap.test('cleanup test SMTP server', async () => {
+  if (testServer) {
+    await stopTestServer(testServer);
+  }
+});
+
+export default tap.start();