Where do a find the Code Mailer UI?

I'm not the original author of the module, and I became the maintainer later.
As of now, there is no UI to send emails like you'd do in email clients. However, the mailer module provides an action that is both Rules and core Actions compatible, to send an email.

If we need a dedicated UI to send mass emails, that becomes out of the module scope. Also, there is VBO integration that can help you in sending mass emails, though you will need some hacky workaround to make it easily usable.

But where is this action?

I don't see it when you create a new action in rules.

P.S. I also understand that you can create an advanced system action, outside of rules, to have a code mailed by listing a number of email addresses ... but how to you execute this action and what are the conditions for doing so?

I've scoured every interface: rules, system, actions, etc, and cannot find where to actually send the email.

If it in fact can be sent through a rules action, then there should be some regcode action listed under "actions" when you create a new rule. What am I missing here?