I'm a long-term Outlook user looking to move from Outlook 2013 (now unsupported by MS) to Thunderbird. I've looked at all Mozilla documentation, as well as Google Search and can't seem to find a full understanding of the migration process. I have tried to manually do so using the Tools>Import in Thunderbird, but I continually get an error message that "the current mail client cannot fulfill the messaging request". (Yes, Outlook is my default mail client). Also, I'm now seeing the following on my Thunderbird home page: '''Secure connection failed''' live.mozillamessaging.com uses an invalid security certificate. The certificate is not trusted because the issuer certificate is unknown. Can anyone help an Outlook refugee? Thanks in advance. Julian