Thunderbird 3.x has a 'helpful' automatic account setup wizard. The bad news is that it is about as competent as Rincewind.

I want to set up a new POP3 account, so I do File | New | Mail Account. It asks me for some basic settings (like name, email address and password). Whether or not I give it a password, it then shows me the 'helpful' automatic account config page.

It finds, in microseconds, that there is an IMAP server at the domain. Which there is. But regardless of whether I press 'start over' or 'manual setup' to get to the manual setup page of the account settings, I get to the same display. Which insists that it's going to be an IMAP account rather than a POP3 one and there's nothing I can do about it. Why would someone want a POP3 account when IMAP works?

It doesn't fucking matter why, it's what I want.

What it turns out you have to do is press a 'stop' button in the wizard and follow the instructions here.

Yeah, pressing 'stop' rather than 'manual setup' to get to the real manual setup… Have they been getting code from some of the people responsible for Outlook?