Add `header_instructions` overridable translation for email headers.

app/views/email/notification.html.erb

@@ -1,5 +1,7 @@
 <div id='main' class=<%= classes %>>
 
+  <div class='header-instructions'>%{header_instructions}</div>
+
   <%= render partial: 'email/post', locals: { post: post } %>
 
   <% if context_posts.present? %>

config/locales/server.en.yml

@@ -1894,6 +1894,7 @@ en:
       title: "Unsubscribe"
       description: "Not interested in getting these emails? No problem! Click below to unsubscribe instantly:"
 
+    header_instructions: ''
     reply_by_email: "To respond, reply to this email or [visit the topic](%{base_url}%{url}) in your browser."
     visit_link_to_respond: "To respond, [visit the topic](%{base_url}%{url}) in your browser."
 
@@ -1934,6 +1935,8 @@ en:
     user_replied:
       subject_template: "[%{site_name}] %{topic_title}"
       text_body_template: |
+        %{header_instructions}
+
         %{message}
 
         %{context}
@@ -1944,6 +1947,8 @@ en:
     user_quoted:
       subject_template: "[%{site_name}] %{topic_title}"
       text_body_template: |
+        %{header_instructions}
+
         %{message}
 
         %{context}
@@ -1954,6 +1959,8 @@ en:
     user_mentioned:
       subject_template: "[%{site_name}] %{topic_title}"
       text_body_template: |
+        %{header_instructions}
+
         %{message}
 
         %{context}
@@ -1964,6 +1971,8 @@ en:
     user_group_mentioned:
       subject_template: "[%{site_name}] %{topic_title}"
       text_body_template: |
+        %{header_instructions}
+
         %{message}
 
         %{context}
@@ -1974,6 +1983,8 @@ en:
     user_posted:
       subject_template: "[%{site_name}] %{topic_title}"
       text_body_template: |
+        %{header_instructions}
+
         %{message}
 
         %{context}
@@ -1984,6 +1995,8 @@ en:
     user_posted_pm:
       subject_template: "[%{site_name}] [PM] %{topic_title}"
       text_body_template: |
+        %{header_instructions}
+
         %{message}
 
         %{context}

lib/email/message_builder.rb

@@ -28,6 +28,8 @@ module Email
       }.merge!(@opts)
 
       if @template_args[:url].present?
+        @template_args[:header_instructions] = I18n.t('user_notifications.header_instructions')
+
         if @opts[:include_respond_instructions] == false
           @template_args[:respond_instructions] = ''
         else
@@ -65,6 +67,14 @@ module Email
         html_override.gsub!("%{unsubscribe_link}", "")
       end
 
+      header_instructions = @template_args[:header_instructions]
+      if header_instructions.present?
+        header_instructions = PrettyText.cook(header_instructions).html_safe
+        html_override.gsub!("%{header_instructions}", header_instructions)
+      else
+        html_override.gsub!("%{header_instructions}", "")
+      end
+
       if response_instructions = @template_args[:respond_instructions]
         respond_instructions = PrettyText.cook(response_instructions).html_safe
         html_override.gsub!("%{respond_instructions}", respond_instructions)