The Instapaper merge tag lets you add automatic “Read Later” buttons to your RSS-to-email and normal newsletters. It’s handy if you tend to write lengthy articles in your newsletters, or if a high percentage of your subscribers read email on a mobile device and may want to save your content for later (check out our mobile study for some research on that).
There are two ways to use the Instapaper merge tag: the first saves your entire newsletter to Instapaper, and the second saves content outside your newsletter. To create a Read Later button that saves your newsletter content, use the merge tag in its simplest form:
Just place that tag wherever you’d like the button in your template.