Currently Claws Mail has no feature to warn the user that a weak TLS cipher is in use or to disable usage of weak ciphers. Having one would improve security. Example: RSS feed https://news.opensuse.org/feed/ for which the host uses weak ciphers only and CM shows no warning about it: https://www.ssllabs.com/ssltest/analyze.html?d=news.opensuse.org&hideResults=on