Important Security Firmware Update from NETGEAR from sender security@e.netgear.com

Details would depend on the mail headers and link locations - or Netgear revealing that they've sent this mail; a first hint might be not following any links and searching for an update for your device and its release notes on https://www.netgear.com/support/ yourself.

My gut instincts strongly suggest this probably being a spam/ scam attempt, trying you to run their malicious software or access your access credentials on their site.

So don't do either, ignore the mail and don't click any links (nor mine given above), and just make sure that you're running the most recent firmware based on Netgear's official support site (and/ or running the update search in the webinterface of your router, respectively the orbi/ nighthawk app).