Mail no longer connects to server

I recently change my host. I set up the old email accounts I've been using for years.

It works fine when I send and get mail from the browser.

But Mail no longer works at all. All I get is a never ending drop down box telling me it can't connect to server and asks for the password.

I've checked many times and the password is fine. I've tried Pop and IMAP with all settings according to instructions. I unchecked and rechecked SSL.

I've fixed permissions. I've restarted. I've dumped all the old accounts and created new ones from scratch.

Nothing works!

I'm on the latest Yosemite.

Thanks.