update

readme.hints.md

@@ -260,4 +260,66 @@ tap.start();
 - Server generates self-signed certificates automatically for testing
 - Default test port is 2525
 - Connection timeout is typically 10 seconds
-- Always check for complete SMTP responses (ending with space after code)
+- Always check for complete SMTP responses (ending with space after code)
+
+## SMTP Implementation Findings (2025-05-25)
+
+### Fixed Issues
+
+1. **AUTH Mechanism Implementation**
+   - The server-side AUTH command handler was incomplete
+   - Implemented `handleAuthPlain` with proper PLAIN authentication flow
+   - Implemented `handleAuthLogin` with state-based LOGIN authentication flow
+   - Added `validateUser` function to test server configuration
+   - AUTH tests now expect STARTTLS instead of direct TLS (`secure: false` with `requireTLS: true`)
+
+2. **TLS Connection Timeout Handling**
+   - For secure connections, the client was waiting for 'connect' event instead of 'secureConnect'
+   - Fixed in `ConnectionManager.establishSocket()` to use the appropriate event based on connection type
+   - This prevents indefinite hangs during TLS handshake failures
+
+3. **STARTTLS Server Implementation**
+   - Removed incorrect `(tlsSocket as any)._start()` call which is client-side only
+   - Server-side TLS sockets handle handshake automatically when data arrives
+   - The `_start()` method caused Node.js assertion failure: `wrap->is_client()`
+
+4. **Edge Case Test Patterns**
+   - Tests using non-existent `smtpClient.connect()` method - use `verify()` instead
+   - SMTP servers must handle DATA mode properly by processing lines individually
+   - Empty/minimal server responses need to be valid SMTP codes (e.g., "250 OK\r\n")
+   - Out-of-order pipelined responses break SMTP protocol - responses must be in order
+
+### Common Test Patterns
+
+1. **Connection Testing**
+   ```typescript
+   const verified = await smtpClient.verify();
+   expect(verified).toBeTrue();
+   ```
+
+2. **Server Data Handling**
+   ```typescript
+   socket.on('data', (data) => {
+     const lines = data.toString().split('\r\n');
+     lines.forEach(line => {
+       if (!line && lines[lines.length - 1] === '') return;
+       // Process each line individually
+     });
+   });
+   ```
+
+3. **Authentication Setup**
+   ```typescript
+   auth: {
+     required: true,
+     methods: ['PLAIN', 'LOGIN'],
+     validateUser: async (username, password) => {
+       return username === 'testuser' && password === 'testpass';
+     }
+   }
+   ```
+
+### Progress Tracking
+- Fixed 8 tests total (as of 2025-05-25)
+- 30 error logs remaining in `.nogit/testlogs/00err/`
+- Edge cases, email composition, error handling, performance, reliability, RFC compliance, and security tests still need fixes