In 2015 and i have a dane compatible servers (my blog) running the latest and greatest in tls support which is version 1.2 and not version 1.0. I thought i did not need the old version, they still use ssl v3 as well
I run a script and see a certain address with thousands of connects but no mail, and one day i guess they use the thing i do not have. Grudgingly i enable tlsv1 on one mail server.
That should fix it.