Index: app/models/mailer.rb
===================================================================
--- app/models/mailer.rb	(revision 14155)
+++ app/models/mailer.rb	(working copy)
@@ -389,7 +389,7 @@
     headers.reverse_merge! 'X-Mailer' => 'Redmine',
             'X-Redmine-Host' => Setting.host_name,
             'X-Redmine-Site' => Setting.app_title,
-            'X-Auto-Response-Suppress' => 'OOF',
+            'X-Auto-Response-Suppress' => 'All',
             'Auto-Submitted' => 'auto-generated',
             'From' => Setting.mail_from,
             'List-Id' => "<#{Setting.mail_from.to_s.gsub('@', '.')}>"
Index: test/unit/mailer_test.rb
===================================================================
--- test/unit/mailer_test.rb	(revision 14155)
+++ test/unit/mailer_test.rb	(working copy)
@@ -197,7 +197,7 @@
     Mailer.deliver_issue_add(issue)
     mail = last_email
     assert_not_nil mail
-    assert_equal 'OOF', mail.header['X-Auto-Response-Suppress'].to_s
+    assert_equal 'All', mail.header['X-Auto-Response-Suppress'].to_s
     assert_equal 'auto-generated', mail.header['Auto-Submitted'].to_s
     assert_equal '<redmine.example.net>', mail.header['List-Id'].to_s
   end