Call me naive, but I don't believe that I'm going to wake up tomorrow and ChatGPT.com and Claude.ai are going to be hard down and never come back. Same as Gmail, which is an entirely different corporation. I mean, they could, but it doesn't seem insane to use Gmail for my email, and that's way more important to my life functioning than this new AI thing.

Email is deterministic and portable. Export to a standard format and import somewhere else.