Did you ever get any answers to this? I have been unable to use either Apple Mail or Thunderbird with Eskimo (as IMAP) on this computer, because neither program can make a connection with Eskimo's SMTP server. I do have Mail successfully working with Eskimo on another computer, where I set it up years ago; I have no idea why that worked way back then, when I can't even set up an account in Mail on this computer now, because the setup wizard fails to connect to Eskimo's SMTP server and has to be force-quit. I can read eskimo email with Thunderbird, but I can't send mail with it.
I have queried support, but haven't heard back yet.
The eskimo certificate is a self-made one on the mail server, and Apple isn't happy with that.