Apparently hotmail.com started using another certificate for their TLS sessions. According to your log Microsoft issued the certificate themselves and you don't have their root certificate in your config. Download the root certificate and import it.
__________________________________ I'm just a user of The Bat! I don't work for Ritlabs.
So do you know where to download certificate from? Does other e-mail clients nag user with this nonsense? Should I contact support and open ticket making my post redundant, and solution not available to others?