Newsletter Archive Addon GPL Overview:

The Archive Addon enables a special shortcode that can be used in a WordPress page to show the sent newsletter archives. The shortcode to use is (without inner spaces)

On the first page show, the list of sent newsletters appears made of the subject and the sending date. Clicking on a newsletter, it is shown with a heading 2 title (H2) containing the subject and a frame containing the real text. The frame is required since every newsletter is a real and complete HTML page and cannot be embedded directly into the page: the blog style would affect (negatively) its appearance.

Alternatively, you can set to show the newsletter content on a new browser page, see the addon configuration.