Thunderbird stopped working. I received the following message - "Add Security Exception You are about to override how Thunderbird identifies this site. Legitimate banks, stores and other public sites will not ask you to do this. Location: smtp.optusnet.com.au:25 This site attempts to identify itself with invalid inforation The certificate belongs to a different site, which could mean that someone is trying to impersonate this site Permanently store this exception" I have clicked on 'Confirm Security Exception" but I still can't send or receive emails.