Wherever you rent your box, you must choose the Ubuntu 14.04 x64 operating system. Most any cloud provider will do, but not Amazon Web Services because its network is often blocked to prevent users from sending spam.
-Each cloud provider will have different instructions for setting up “reverse DNS.” As described above, Digital Ocean's method is to give your droplet the same name as your hostname, but other providers may use differentmethods. You must follow your cloud provider’s instructions for setting the reverse DNS of your box to your box’s hostname.
+Each cloud provider will have different instructions for setting up “reverse DNS.” You must follow your cloud provider’s instructions for setting the reverse DNS of your box to your box’s hostname. At Digital Ocean you set the name of your droplet to the box’s hostname, as mentioned above.
Josh’s box’s reverse DNS is set to the same as the box’s hostname: box.occams.info.