fix: Resolve Exchange email server self-signed certificate error

- Add TLS configuration to accept self-signed certificates
- Disable TLS/STARTTLS for port 25 when SMTP_SECURE=false
- Add ignoreTLS option for Exchange servers on port 25
- Update .env.example with Exchange-specific configuration
- Create comprehensive EMAIL_CONFIGURATION.md guide
- Support both Exchange internal servers and modern SMTP servers

This fixes the "self-signed certificate" error when connecting
to Microsoft Exchange servers on port 25 without TLS.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

.env.example

@@ -23,11 +23,18 @@ MINIO_ACCESS_KEY=minioadmin
 MINIO_SECRET_KEY=minioadmin
 
 # Email Configuration (for reports)
-SMTP_HOST=smtp.gmail.com
-SMTP_PORT=587
+# For Microsoft Exchange on port 25 without TLS:
+SMTP_HOST=exchange.yourcompany.com
+SMTP_PORT=25
 SMTP_SECURE=false
-SMTP_USER=your-email@gmail.com
-SMTP_PASS=your-app-password
+SMTP_USER=username
+SMTP_PASS=password
+# For Gmail/Office365 with STARTTLS:
+# SMTP_HOST=smtp.gmail.com
+# SMTP_PORT=587
+# SMTP_SECURE=false
+# SMTP_USER=your-email@gmail.com
+# SMTP_PASS=your-app-password
 REPORT_RECIPIENT=info@example.com
 REPORT_SENDER=kopiabackup@example.com