Postmark blog is a blog by Postmark (a transactional email service). They want “tutorials that cover broad topics related to transactional email such as delivery, reputation, design, tools, and testing, as well as tutorials for using Postmark with specific languages and systems such as Python, Rails, Laravel, Node, and so on.” They pay $200 to $300 per tutorial, depending on its complexity. To learn more, visit this page.