I had to use a CSS Inliner building my newsletter on Sitecore….
Basically I wanted to build my newsletter HTML using external css for code re-usability and to enforce my branding style. And I need to inline my CSS before sending to the clients (gmail & outlook ate external css…)
here it come Premailer: https://github.com/milkshakesoftware/PreMailer.Net
One line of code and the magic is done