Send email to contact_email when a new version of Discourse is found. Disable with the new_version_emails setting.

app/mailers/version_mailer.rb

@@ -0,0 +1,14 @@
+require_dependency 'email/message_builder'
+
+class VersionMailer < ActionMailer::Base
+  include Email::BuildEmailHelper
+
+  def send_notice
+    if SiteSetting.contact_email.present?
+      build_email( SiteSetting.contact_email,
+                   template: 'new_version_mailer',
+                   new_version: DiscourseUpdates.latest_version,
+                   installed_version: Discourse::VERSION::STRING )
+    end
+  end
+end