Which link should you use from Site Contents?

Explanation/Reference:
Note:
Create the site mailbox
When you’ve decided that it is beneficial to have a site mailbox, creating one is very straight-forward. Every time you create a new site in SharePoint 2013 you see the option in the “Get started with your site” menu to “Keep email in context”. Clicking this tile installs the site mailbox app on your SharePoint team site. If you don’t see this option on your site just click “Site Contents”, and add the “Site Mailbox” app under the app listings.