Consegui migrar com sucesso uma lista do Mailman seguindo o procedimento de
Agora há muitos usuários em estágio provenientes da lista do Mailman. O que os usuários precisam fazer para fazer login na nova comunidade Discourse?
To sign on staged users must create a new account “sign up” using the same email from the mailing list. They’ll receive an email verifying that they own the address entered, and once verified they’re good to go.
It’s all about the email address matching. Remember that to Discourse, email address = identity. This is absolutely central to how Discourse works.