diff --git a/core/admin/mailu/models.py b/core/admin/mailu/models.py
index 2bd0f04f..cac1728d 100644
--- a/core/admin/mailu/models.py
+++ b/core/admin/mailu/models.py
@@ -12,6 +12,7 @@ import os
 import glob
 import smtplib
 import idna
+import dns
 
 
 class IdnaDomain(db.TypeDecorator):