Is there way to trigger a reactive event in a ShinyApp over the internet (e.g. trough an email)?

Question

My friend and I are working in the development of a ShinyApp for our community. The purpose of the App is to create a distribution mailing list to share job opportunities. There are two tabs, a tab to subscribe/unsubscribe to the mailing list and a second tab to post a job opportunity.

Our app now is able to send the job offer posted automatically to all the recipients in the current mailing list. However, we want to be able to control the content of what is posted. So, we want to be able to preapprove the mails before sending to the mailing list.

Is there a way to get a responsive email from which the administrators can just press an "Accept" or "Decline" button to either deliver or reject the job offer?

We have certain ideas:

• Send the response to our ShinyApp and deliver or reject the message from our ShinyApp. Can Shiny receive an input (e.g. an action button) from outside the App?
• Create a customized message that Gmail somehow understands to deliver/reject the message automatically.