Environment Variable Based Configuration With Multi Source Fallback

via “environment-variable-based configuration with multi-source fallback”

** - This server enables users to send emails through various email providers, including Gmail, Outlook, Yahoo, Sina, Sohu, 126, 163, and QQ Mail. It also supports attaching files from specified directories, making it easy to upload attachments along with the email content.

Unique: Implements a three-tier configuration hierarchy (CLI > environment variables > defaults) that separates static provider configurations (email.json) from dynamic credentials (environment variables), enabling secure deployment patterns where secrets are never stored in code or configuration files.

More secure than hardcoded credentials and simpler than full configuration management systems like Consul or etcd, though less flexible than runtime configuration APIs.