I have configured Tesco.net messages to be picked up in Mozilla Thunderbird, but whether or not I am using the program I keep getting a box to tell me to 'add security exception', because Tesco is attempting to identify itself with invalid information. The security information is, in fact, correct, but although I click the 'confirm security exception' button, the program won't accept it. Sometimes, I have to click the button 10 or 15 times before the box disappears, only to reappear several times during the course of the day. How can I stop this?