Postmark has introduced a feature called transactional email templates that provides tools to address common challenges when creating emails. The templates offer a set of starter templates with best practices for transactional email, and an editing environment that allows users to preview and test the content of their emails. Postmark Templates also include a powerful feature that suggests a model for all values required by the template, making it easy to create dynamic emails. The templating language is based on Mustache, but with added features such as 'each' syntax for handling arrays of values and complex keys. Postmark Templates are now open source, allowing users to integrate them into their email workflow even if they use an Email Service Provider other than Postmark.