The use of TLS in sending email is a very new thing on the Internet and formal standards have not yet been set. Not all email servers in the world support it yet and it is estimated that less than half do. Our servers are set to use encryption whenever possible, but to automatically drop levels of security all the way down to plain text depending on the capabilities and protocols of the two servers that are communicating. Since there are no formal standards for encryption, it is not required by anyone, nor does it affect email deliverability.

TLS 1.0 is not formally deprecated by NIST. "All major inbox providers" do not have the authority to deprecate an internationally accepted Internet standard, only NIST (National Institute of Standards and Technology) can do that. If an email provider does not want to accept TLS 1.0 encrypted communications, then they can simply disable it on their server. In the meantime, we will use the best transmission encryption that the recipient server will accept.