[Plugin: Custom Post Type UI] Trying to add_action to a custom post type

Hello. I currently use the custom post-type which works great. We’d like to add in the ability so that when a post is published, an email will also be sent out as part of an announcement to our community (we use WP as a series of announcement/notification system).

I’ve found another plug-in that seems to fit the bill of what we are trying to do: https://worth2read.org/2010/02/21/wordpress-plugin-send-notification-by-email-when-a-post-is-published/

The downside is that it only shows a meta-box for the email option to normal posts and not custom post types. It looks to be because the only action in the code is:
add_action('publish_post', 'send_email');

I’m a newbie at WP but I figured that publish_post meant a normal post. What would be the keyword for either ALL of my custom posts or just a single custom post?

Can anyone point me in the right direction please? Thank you!!