To get my head around OAUTH2 I bought a book with the same title by Matt Biehl. This gives a good overview on the internals and use of OAUTH2 This post is about accessing Gmail accounts using Googles OAUTH2 authorisation process. Essentially this is a conversation involving multiple parties/servers and goes something like this : register app with google app sends request to googles oauth2 server : I would like to get access to emails from a specific account oauth se