Microsoft has effectively retracted a policy announcement from last Friday that. After further consideration, they will continue issuing the emails.
The announcement last Friday blamed "...changing governmental policies concerning the issuance of automated electronic messaging..." for the decision. It was clear that the government policy at issue was a new Canadian anti-spam law, scheduled to go into effect July 1. Microsoft recommended that users switch to their RSS feeds instead.
This afternoon a Microsoft spokesperson issued this statement: "On June 27, 2014, Microsoft notified customers that we were suspending Microsoft Security Notifications due to changing governmental policies concerning the issuance of automated electronic messaging. We have reviewed our processes and will resume these security notifications with our monthly Advanced Notification Service (ANS) on July 3, 2014."
The ANS this Thursday is the advance notification of updates to be released on July, i.e. Patch Tuesday.