By the way, I just checked, Gmail works without problems over Tor (both Web and IMAPS).
Using Gmail over Tor when they already know who you are is self-defeating. Try to register an anonymous Gmail account using Tor.
Doable. They require a phone number for verification, but that's the same with and without Tor. Besides, if you want an anonymous email, use _anything but Gmail_, eg. ProtonMail.
Providing you phone number during registration = registration is not anonymous, so anonymous registration of a Gmail account using Tor is NOT doable.
Last time I tried, this did not work. I provided the SMS number in a Tor registration attempt and Gmail said we cannot register you "at this time", without even trying to send me an SMS.
Protonmail is exactly the same thing, if you want to register a free account you need to provide your phone number. You can register "anonymously" in ProtonMail only for paid account, and even if you are willing to pay for anonymity, you need to pay in bitcoin which ultimately discloses you identity - so again, not anonymous.