Starting on Jan 16, 2020 (next week), ESS will no longer accept connections on SSL v3. Additionally on Jun 1, we’ll drop support for TLS v1.0 and v1.1. These are extremely old protocols that have lots of security vulnerabilities.
This does mean that if any sender sends an email to ESS using these protocols that email will be rejected. If you are aware of any senders that are still using these protocols, please advice them to upgrade.