I have been using Thunderbird quite happily for several months for the e.mail on my wife's business. Then today we received a pop up entitled '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.' I have checked my pop 3 settings and they all look ok. It seems very odd that it would suddenly do this which makes me concerned that this is a case of someone trying to hack / impersonate the server that hosts our e.mail - how do I rectify it? The email is being run on a home pc using windows 10. E.mails are still being received on an ipad and iphone (not using thunderbird).