The current DNS is unnecessarily slow and suffers from inability to deploy new features. To remediate these problems, vendors of DNS software and also big public DNS providers are going to remove certain workarounds on February 1st, 2019.
This change affects only sites which operate software which is not following published standards. Are you affected?
Find out at https://dnsflagday.net/
Presentation:
Flag Day means a software change that is not backward-compatible, especially in a network system where upgrade is scheduled early and everybody must deploy upgrade at (before) the date, or the system will stop working. It came into use when a change was made to the definition of the ASCII character set during the development of Multics. The change was scheduled for Flag Day (a U.S. holiday, Flag Day (United States) - Wikipedia ), June 14, 1966.
See Jargon File.