If your IMAP email stops working on your Thunderbird mail program after you have installed Kaspersky you should try the following steps:
Open software and then click Settings > Additional > Network > Proxy server settings > Activate do not use proxy server.
If this does not work do the next step:
Back to settings > Web Anti Virus > Advanced Settings > Configure Trusted Web Pages > add - Enter the URL of your website, Right click on status and select Activate.