I just found out about this and I've had a couple of clients who have domain issues related to this. In a nutshell:
Check for domain registrar compliance:
The current DNS is unnecessarily slow and inefficient because of efforts to accommodate a few DNS systems that are not in compliance with DNS standards established two decades ago.
To ensure further sustainability of the system it is time to end these accommodations and remediate the non-compliant systems. This change will make most DNS operations slightly more efficient, and also allow operators to deploy new functionality, including new mechanisms to protect against DDoS attacks.
DNS software and service providers listed on this site have agreed to coordinate removing accommodations for non-compliant DNS implementations from their software or services, on or around February 1st 2019. This change will affect only sites operating non-compliant software.