These newsletters have always been hard to create as regular web HTML is not properly read by web email interfaces and email clients. I thought that the simplest solution would be to use a web page that would serve as a web version of the newsletter and turn it somehow into newsletter HTML.
To fix issues with display of special language characters once and for all
there's a solution: use Unicode UTF-8 everywhere. If everything is set up to use Unicode, you can use mostly every language in your application.
I found a standard Yii app's protected folder structure nearly perfect. With a few simple moves and a little bit change to the code, I managed to bring it to the level, which I found as fully perfect. I want to share my point of view, in case someone would like to use this structure as well.