Here's an idea that I thought was already included in stock SugarCRM but apparently not.
On each newsletter, you usually add a "view it in your browser" link to allow mobile users to actually access the entire newsletter without any limitation from their email client.
In general, you simply link the archive file and it opens up the newsletter in the browser. Or, if you wish to share your newsletter with non-subscribers (via social media for example) you simply use the archive file which works kinda like a landing page.
However, it seems like SugarCRM does not archive the HTML file itself for an external use. When creating an HTML file in SugarCRM, we could have the option to flag the model as final (meaning, ready to be sent out to subscribers after tests have been conducted). Once flagged as final, SugarCRM could create a direct link to the HTML file (for external use).