FEATURE: add a global notice whenever emails are disabled (disable_emails site setting)

app/assets/javascripts/discourse/components/global-notice.js.es6

@@ -10,6 +10,10 @@ export default Ember.Component.extend(StringBuffer, {
       notices.push(I18n.t("read_only_mode.enabled"));
     }
 
+    if (this.siteSettings.disable_emails) {
+      notices.push(I18n.t("emails_are_disabled"));
+    }
+
     if (Discourse.User.currentProp('admin') && this.siteSettings.show_create_topics_notice) {
       var topic_count = 0,
           post_count = 0;

config/locales/client.en.yml

@@ -103,6 +103,8 @@ en:
 
     topic_admin_menu: "topic admin actions"
 
+    emails_are_disabled: "Administrators have disabled emails."
+
     edit: 'edit the title and category of this topic'
     not_implemented: "That feature hasn't been implemented yet, sorry!"
     no_value: "No"

config/site_settings.yml

@@ -428,7 +428,9 @@ email:
     enum: 'TrustLevelSetting'
   email_prefix: ''
   email_site_title: ''
-  disable_emails: false
+  disable_emails:
+    default: false
+    client: true
   strip_images_from_short_emails: true
   short_email_length: 2800