You did not mention what version you are using but in some versions of moodle (I am using 1.9.1) you can link a lesson to another activity.
First create a resource (link to a file or webpage), then create your tutorial as a lesson and link the resource that links to gmail at the end of the lesson. The weakness of this approach is that there isn't a way for you to check if they really signed in to gmail. You can ask the student to email you from gmail, I suppose.