I have been looking around for how to create a webhook that is triggered when an email is sent or received in Gmail. For example someone sends an email, that email gets POSTed as a JSON object to one of my applications. I have found many middleman applications/services that do this (I found a tool that offers all the functionality I want, but it costs money), but I can't find any documentation on how to actually do this myself so I don't need to pay for it.
Is this possible?
After some research the best solution I could find was to use the gmail API
To achieve the functionality that zapier offers you would have to have a service or something polling google and querying the status of a users in box. There are also a couple of ways to trigger calls to code, but I do not think this is what zapier does. Check the gmail API for more information.