diff --git a/trac/notification/mail.py b/trac/notification/mail.py
index 4c008f3deb..95a2768391 100644
--- a/trac/notification/mail.py
+++ b/trac/notification/mail.py
@@ -646,7 +646,8 @@ def _do_send(self, transport, event, message, cc_addrs, bcc_addrs):
             set_header(message, 'Cc', addresses=cc_addrs)
         if bcc_addrs:
             set_header(message, 'Bcc', addresses=bcc_addrs)
-        set_header(message, 'Reply-To', addresses=[smtp_replyto])
+        if smtp_replyto:
+            set_header(message, 'Reply-To', addresses=[smtp_replyto])
 
         for decorator in self.decorators:
             decorator.decorate_message(event, message, self._charset)
diff --git a/trac/notification/tests/mail.py b/trac/notification/tests/mail.py
index 23e8a6289c..7569605a76 100644
--- a/trac/notification/tests/mail.py
+++ b/trac/notification/tests/mail.py
@@ -509,6 +509,22 @@ def test_username_is_email(self):
         self._assert_equal_sets(['cc@example.org'],
                                 self._cclist(message['Cc']))
 
+    def test_replyto(self):
+        config = self.env.config
+        config.set('notification', 'smtp_replyto', 'replyto@example.org')
+        self._notify_event('blah')
+        history = self.sender.history
+        from_addr, recipients, message = history[0]
+        self.assertEqual('replyto@example.org', message['Reply-To'])
+
+    def test_replyto_empty(self):
+        config = self.env.config
+        config.set('notification', 'smtp_replyto', '')
+        self._notify_event('blah')
+        history = self.sender.history
+        from_addr, recipients, message = history[0]
+        self.assertNotIn('Reply-To', message)
+
 
 class RecipientMatcherTestCase(unittest.TestCase):