'Invalid Certificate detected'.

Hello Having read good reviews of Mozilla Thunderbird, I thought I would use it as my email application. However, whenever I start Thunderbird I get I warning from Kaspersky anti virus 'Invalid Certificate detected'. “SSL connection with invalid certificate detected. Certificate issued for: pop3.tiscali.co.uk Certificate error: Invalid name of certificate. Either the name is not on the allowed list, or was explicitly excluded. Application: Thunderbird” I have followed the instructions in “Support kaspersky.com/Software compatibility/How to add the Kaspersky Lab root certificate to Thunderbird certificate storage” in order to import the certificate 'Kaspersky Lab Root CA.cer' 'to Thunderbird. However, I am still getting the same warning message when I start Thunderbird – how can I prevent this warning from popping up? Barry Pilkington