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

The authentication account should have a permanent stable identifier that should be the provider's responsibility to issue and manage.

Everything else including email and username should be changeable (provided there's no conflict with other accounts)

> (provided there's no conflict with other accounts)

Couldn't you use this to figure out which emails have registered with Claude?

You can do this on almost every online service by trying to create an account with an email that already has an account.