I'm subscribed to about a dozen "newsletters" of various types, but I thought I'd mention the top two.
Naked Security, from Sophos, is regularly the best of all the newsletters I get. Not only is it reliable, with reasonable editorial content, but the choice of topics and stories is regularly the best: significant and important issues. You can look at it on the Web page, but, if you scroll down a bit, you'll find the "Get the latest security news in your inbox" dialogue, where you can submit your email address and get a daily newsletter. (You can also subscribe to their Twitter account.)
Second best (and it's a close run thing as to which is best) is, oddly, the Security News Digest from the CISO's office of the Province of BC. Gary and his gang of civil servants have been doing a great job in terms of security awareness and events, and, on a weekly basis, produce a really solid newsletter abstracting news stories from the media. Again, a very good choice of the most important and significant stories. To subscribe, send email to OCIOSecurity@gov.bc.ca asking to be put on the distribution list for the Security News Digest.
And, as long as we are talking email, if you've got your CISSP, you can always subscribe to the CISSPforum via:
https://www.noticebored.com/html/cisspforumfaq.html#Subscribing
or
https://groups.io/g/cisspforum
or
https://community.isc2.org/t5/Welcome/CISSPforum-replacement/m-p/11006
............
Other posts: https://community.isc2.org/t5/forums/recentpostspage/user-id/1324864413
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http://www.noticebored.com/html/cisspforumfaq.html#Friday or
https://blogs.securiteam.com/index.php/archives/1468
