diff --git a/app/models/mailer.rb b/app/models/mailer.rb
index dc155648e..2364774fb 100644
--- a/app/models/mailer.rb
+++ b/app/models/mailer.rb
@@ -721,7 +721,7 @@ class Mailer < ActionMailer::Base
     hash = [
       "redmine",
       "#{object.class.name.demodulize.underscore}-#{object.id}",
-      timestamp.strftime("%Y%m%d%H%M%S")
+      timestamp.utc.strftime("%Y%m%d%H%M%S")
     ]
     if rand
       hash << Redmine::Utils.random_hex(8)
diff --git a/test/unit/mailer_test.rb b/test/unit/mailer_test.rb
index 7af853b67..d3ff87418 100644
--- a/test/unit/mailer_test.rb
+++ b/test/unit/mailer_test.rb
@@ -343,6 +343,17 @@ class MailerTest < ActiveSupport::TestCase
     end
   end
 
+  def test_timestamp_in_message_id_should_be_utc
+    zone_was = Time.zone
+    issue = Issue.find(3)
+    %w(UTC Paris Tokyo).each do |zone|
+      Time.zone = zone
+      assert_match /^redmine\.issue-3\.20060719190727\.[a-f0-9]+@example\.net/, Mailer.token_for(issue)
+    end
+  ensure
+    Time.zone = zone_was
+  end
+
   test "#issue_add should notify project members" do
     issue = Issue.find(1)
     assert Mailer.deliver_issue_add(issue)