If you look at the examples, they all look like adding extra functionality to your inbox, not to the content of the emails you send.
So it doesn't sound like "I'll send you this email that you can only access if you have gmail AND this specific add-ons", more like "when you open an email, the add-on shows relevant information from your internal CRM system as well as canned responses".
So it doesn't sound like "I'll send you this email that you can only access if you have gmail AND this specific add-ons", more like "when you open an email, the add-on shows relevant information from your internal CRM system as well as canned responses".