When setting up an new account in Thunderbird, a password is required after entering the email address. How is that password used? One can infer that it is used in the last step after validating the domain's POP3 and SMTP port and connection verification values. What is it validated against? Does it require that the mail servers at the named domain have the account set up with a password? I'm having trouble setting up accounts with addresses established at the Fastmail.com domain. I need the answer in order to clarify the problem with Fastmail. TIA