* [Mailtrap Node.js client v5.0.0](https://github.com/mailtrap/mailtrap-nodejs) – Node.js client for sending transactional and bulk emails with sandbox mode, attachments, and API token-based authentication.

* [Premailer v1.32.0](https://github.com/premailer/premailer) – Converts CSS into inline styles, fixes relative paths, checks CSS for email-client compatibility, and generates plain-text output.