When I install Thunderbird, either the Microsoft-approved version (129mb) or directly from thunderbird site (119mb), I get the attached error message. It doesn't matter if I click Cancel or click "Confirm Security Exception", I get the same result. The initial result is that I go into my new Thunderbird email account and all appears fine). But when I try to send an email, I get that same message again (altho with a different 3-digit number following imap.gmail.com) followed by a "message couldn't be sent" error message.