For other’s benefit, there is a difference between the Quick Action type of “Send Email”, which is available to add to the layouts of any object type, and a special Case-Feed specific “Email” action which has a more robust email editor which, among other options, lets you select an Email Template to use as the base for your email. This Action type appears to be limited to Feed-based Page Layouts, which are only available on the Case object. In certain circumstances this Quick Action is available to add to the Quick Actions publisher for a Case Page Layout, but if it’s not, the workaround is to use a Custom Visualforce Quick Action, which shows a Visualforce Page that contains the component, which replicates the functionality of the “Email” Quick Action which may not be available (and which is, confusingly, different from the “Send Email” Quick Action type which you can use to add your own “Send Email” actions).
Here is an example of what the Visualforce Page would look like to allow you to create a Custom Visualforce Quick Action:
NOTE: This will only work for the Case object. To get it to work with other objects, you’ll need to adjust the Visualforce Page code above.
This will produce something like the following:
