Anthropic: You can't change your Claude account email address

Anecdote, but I've never been able to use Claude (directly) because their defense systems seem overly sensitive to your email address. I signed up for Claude using a relatively new Outlook email address that I set up for an independent purpose. My account got instabanned. Like, I couldn't proceed at all. I don't even know what the Claude UI looks like. All I could do was appeal using a Google Form.

I appealed and got a standard Google Forms response. There was no follow-up after that. It never got fixed and I never tried again... plenty of free, more accessible fish out there, and various agents like Copilot give me access to Sonnet anyway.

But now I wonder, what is it about the account that triggered this block. If it was because of the reputation of the account, how did Anthropic even know that this account was created a few weeks ago?

I have never been able to use it because they require a phone number during registration and would always reject mine.