add the service desk mailer

app/mailers/emails/ee/service_desk.rb

+module Emails
+  module EE
+    module ServiceDesk
+      def service_desk_thank_you_email(issue_id)
+        setup_service_desk_mail(issue_id)
+
+        mail_new_thread(@issue, service_desk_options(@support_bot.id))
+      end
+
+      def service_desk_new_note_email(issue_id, note_id)
+        @note = Note.find(note_id)
+        setup_service_desk_mail(issue_id)
+        mail_answer_thread(@issue, service_desk_options(@note.author_id))
+      end
+
+      private
+
+      def setup_service_desk_mail(issue_id)
+        @issue = Issue.find(issue_id)
+        @project = @issue.project
+        @support_bot = User.support_bot
+
+        @sent_notification = SentNotification.record(@issue, @support_bot.id, reply_key)
+      end
+
+      def service_desk_options(author_id)
+        {
+          from: sender(author_id),
+          to: @issue.service_desk_reply_to,
+          subject: "Re: #{@issue.title} (##{@issue.iid})"
+        }
+      end
+    end
+  end
+end

app/mailers/notify.rb

@@ -11,6 +11,8 @@ class Notify < BaseMailer
   include Emails::Pipelines
   include Emails::Members
 
+  include Emails::EE::ServiceDesk
+
   helper MergeRequestsHelper
   helper DiffHelper
   helper BlobHelper