[AusNOG] Microsoft have releases a fix for the misbehaviour of their DNS servers.

[Mark Andrews]

If you are using Microsoft for your DNS servers you really should update to
a version that includes this fix from March 19, 2019 monthly updates.

	• Addresses minor issues with unknown options (unknown OPT) in the
	  Extension Mechanisms for DNS (EDNS) for the Windows DNS Server role.

https://support.microsoft.com/en-nz/help/4489893/windows-8-1-update-kb4489893

Older versions have even more egregious misbehaviour, with really old versions
(pre-EDNS support) being flagged as dead by recursive servers as they do not
respond consistently to EDNS queries.  They respond a single time then do not
respond at all for a period of time.

Mark
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742              INTERNET: marka at isc.org