diff --git a/app/models/mailer.rb b/app/models/mailer.rb
index 4f5be2f..fddfef1 100644
--- a/app/models/mailer.rb
+++ b/app/models/mailer.rb
@@ -378,7 +378,7 @@ class Mailer < ActionMailer::Base
     headers 'X-Mailer' => 'Redmine',
             'X-Redmine-Host' => Setting.host_name,
             'X-Redmine-Site' => Setting.app_title,
-            'Precedence' => 'bulk',
+            'X-Auto-Response-Suppress' => 'OOF',
             'Auto-Submitted' => 'auto-generated'
   end
 
diff --git a/test/unit/mailer_test.rb b/test/unit/mailer_test.rb
index 72ed1de..671b7df 100644
--- a/test/unit/mailer_test.rb
+++ b/test/unit/mailer_test.rb
@@ -134,7 +134,7 @@ class MailerTest < ActiveSupport::TestCase
     Mailer.deliver_issue_add(issue)
     mail = ActionMailer::Base.deliveries.last
     assert_not_nil mail
-    assert_equal 'bulk', mail.header_string('Precedence')
+    assert_equal 'OOF', mail.header_string('X-Auto-Response-Suppress')
     assert_equal 'auto-generated', mail.header_string('Auto-Submitted')
   end