This question is related to this Super User question.
What cipher suites do Mail Clients (Thunderbird, Outlook, ...) support?
I know and appreciate the service of SSLLabs where I can see the browsers' capabilities in regard to cipher suites. But also mail clients negotiate TLS connections when loading content via https (e.g. images in newsletters). But I was not able to plug the correct search terms into Google to see which mail client supports which protocol version and which cipher suites.