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Verify what protocol the server supports

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

Verify what protcol the server supports locally

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

What protocol your client is using

$ curl -v --tlsv1 https://www.howsmyssl.com/

Output will show something like:

Your client is using TLS 1.0...