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

postfix/entrypoint.sh

@@ -0,0 +1,15 @@
+#!/bin/sh
+set -e
+
+# Generate main.cf from template with environment variables
+envsubst < /etc/postfix/main.cf.template > /etc/postfix/main.cf
+
+# Generate SASL password file from environment variables
+envsubst < /etc/postfix/sasl_passwd.template > /etc/postfix/sasl_passwd
+
+# Generate Postfix hash
+postmap /etc/postfix/sasl_passwd
+chmod 600 /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db
+
+# Start Postfix in foreground
+exec postfix start-fg