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/main.cf.template

@@ -0,0 +1,21 @@
+# Basic
+myhostname = lists.sasalliance.org
+myorigin = sasalliance.org
+mydestination = $myhostname, localhost.$mydomain, localhost
+
+# Relay through SES
+relayhost = [${SMTP_HOST}]:${SMTP_PORT}
+smtp_tls_security_level = encrypt
+smtp_tls_note_starttls_offer = yes
+
+# SASL auth for SES
+smtp_sasl_auth_enable = yes
+smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
+smtp_sasl_security_options = noanonymous
+
+# Virtual aliases (static for now)
+virtual_alias_maps = hash:/etc/postfix/virtual_aliases.cf
+
+# Other recommended settings
+alias_maps = hash:/etc/aliases
+alias_database = hash:/etc/aliases