Initial commit: Postfix mail server with SES relay

- Containerized Postfix configuration for mailing list management
- Environment-based configuration for SES credentials
- Template-based config generation for flexibility
- Static virtual aliases (Phase 1)
- Prepared for future web interface and SQL backend (Phase 2+)

Features:
- Docker Compose orchestration
- Secure credential management via .env
- Configurable SMTP host/port
- Git-ignored sensitive files
- Comprehensive documentation

.github/copilot-instructions.md

@@ -0,0 +1,97 @@
+# Copilot Instructions: Mail List Manager (Postfix + SES + Web Interface)
+
+## Architecture Overview
+
+This is a containerized mailing list management system built around Postfix as an SMTP relay through Amazon SES. **Currently in Phase 1** with static configuration; **planned expansion** includes web frontend and SQL database for dynamic member management.
+
+**Current Components (Phase 1):**
+- `docker-compose.yaml`: Single-service orchestration with SES credentials
+- `postfix/`: Complete Postfix container configuration  
+- Static virtual aliases system for mailing list distribution
+
+**Planned Architecture (Phase 2+):**
+- Web frontend for list management (view/add/remove members)
+- SQL database backend for member storage
+- Dynamic Postfix configuration generation
+- Multi-service Docker Compose setup
+
+## Configuration Pattern
+
+**Current (Static):** Environment variable substitution for secure credential management:
+
+1. **Credentials Flow**: SES credentials passed via environment → `sasl_passwd.template` → runtime generation in `entrypoint.sh`
+2. **Config Files**: Static configs (`main.cf`, `virtual_aliases.cf`) + dynamic SASL auth file
+3. **Postfix Maps**: Hash databases generated at build time (virtual aliases) and runtime (SASL)
+
+**Future (Dynamic):** Database-driven configuration:
+- Member lists stored in SQL database
+- Web interface for CRUD operations on members
+- `virtual_aliases.cf` generated from database at runtime
+- Postfix reload triggered by configuration changes
+
+## Key Files and Their Roles
+
+- `main.cf`: Core Postfix config - relay through SES, domain settings, security
+- `sasl_passwd.template`: Template for SES authentication (uses `${SES_USER}:${SES_PASS}`)
+- `virtual_aliases.cf`: Static email forwarding rules (one mailing list currently)
+- `entrypoint.sh`: Runtime credential processing and Postfix startup
+
+## Development Workflows
+
+**Building and Running:**
+```bash
+docker-compose up --build    # Build and start mail server
+docker-compose logs -f       # Monitor mail delivery logs
+```
+
+**Adding Mailing Lists (Current):**
+1. Edit `virtual_aliases.cf` with new list → recipients mapping
+2. Rebuild container (postmap runs at build time)
+3. No restart needed for existing virtual alias changes
+
+**Future Web Interface Workflow:**
+1. Access web frontend at configured port
+2. Use CRUD interface to manage mailing lists and members
+3. Changes automatically update database and regenerate Postfix configs
+
+**Testing Mail Delivery:**
+```bash
+# From inside container
+echo "Test message" | mail -s "Subject" community@lists.sasalliance.org
+
+# Check logs for SES relay status
+docker-compose logs postfix | grep -E "(sent|bounced|deferred)"
+```
+
+## Security Considerations
+
+- SES credentials exposed in docker-compose.yaml (consider using Docker secrets)
+- SASL password file permissions set to 600 in entrypoint
+- TLS encryption enforced for SES relay (`smtp_tls_security_level = encrypt`)
+- Only localhost and configured hostname accepted for local delivery
+
+## Configuration Conventions
+
+- **Hostname Pattern**: `lists.sasalliance.org` for mailing lists, origin domain `sasalliance.org`
+- **Virtual Aliases**: Simple format `listname@lists.domain → recipient1, recipient2`
+- **SES Region**: EU West 2 (`email-smtp.eu-west-2.amazonaws.com`)
+- **Port Mapping**: Standard SMTP port 25 exposed to host
+
+## Common Modifications
+
+**Adding Recipients to Existing List (Current):**
+Edit `virtual_aliases.cf`, add comma-separated emails, rebuild container.
+
+**New Mailing List (Current):**
+Add line to `virtual_aliases.cf`: `newlist@lists.sasalliance.org recipients...`
+
+**Credential Updates:**
+Update `SES_USER`/`SES_PASS` in docker-compose.yaml, restart container.
+
+## Migration Considerations
+
+When implementing the web frontend and database backend:
+- Preserve existing `community@lists.sasalliance.org` list during migration
+- Consider migration script to import current virtual aliases into database
+- Plan for zero-downtime deployment with database-driven config generation
+- Web interface should validate email addresses and handle duplicate members