TorBirdy doesn't work with GMail (because it blocks the JavaScript required by OAuth?)
From the tests I did on https://labs.riseup.net/code/issues/11798#note-13 for the integration of TorBirdy in Tails, I understand that it's impossible to configure a GMail account in TorBirdy because TorBirdy blocks the JavaScript needed for OAuth to work.
I'm not questioning the fact that TorBirdy blocks HTML and JavaScript while dealing with emails but would it be possible to have it handle that to make it possible to connect to GMail.
I'm not very fond of GMail myself, it's not friendly to Tor, and cannot provide anonymity but it might still be an option in some scenarios (for example, if you are a journalists working on her own name but travelling to a place where you only want to carry Tails around).