I tried to add a gmail account which has 2step auth with Google authenticator codes enabled. When the oauth dialogue comes up, during the initial account setup, I enter my credentials and finally the six digit  google authenticator code and the dialogue closes before it shows the page where I can grant permission to akonadi to access my account. A few seconds later the oauth window comes back and I have to do the same allover again, again, the dialogue closes immediately after I entered the 6 digit code but before I am prompted to grant permission to akonadi. And so it continues. Only after I disable 2 step verification, it works, but of course that's a security whole that I would rather see fixed.