https://www.ssllabs.com/ssltest
For www.atlassian.com:
Protocols
TLS 1.2 Yes
TLS 1.1 Yes
TLS 1.0 Yes
SSL 3 No
SSL 2 No
s_client This implements a generic SSL/TLS client which can establish a transparent
connection to a remote server speaking SSL/TLS.
$ openssl s_client -connect www.atlassian.com:443 -tls1
$ curl -v --tlsv1 https://www.howsmyssl.com/
Output will show something like:
Your client is using TLS 1.0...