diff --git a/core/admin/mailu/ui/forms.py b/core/admin/mailu/ui/forms.py
index e8302199..48355748 100644
--- a/core/admin/mailu/ui/forms.py
+++ b/core/admin/mailu/ui/forms.py
@@ -37,7 +37,7 @@ class MultipleEmailAddressesVerify(object):
         self.message = message
 
     def __call__(self, form, field):
-        pattern = re.compile(r'^([_a-z0-9\-]+)(\.[_a-z0-9\-]+)*@([a-z0-9\-]{2,}\.)*([a-z]{2,4})(,([_a-z0-9\-]+)(\.[_a-z0-9\-]+)*@([a-z0-9\-]{2,}\.)*([a-z]{2,4}))*$')
+        pattern = re.compile(r'^([_a-z0-9\-]+)(\.[_a-z0-9\-]+)*@([a-z0-9\-]{2,}\.)*([a-z]{2,})(,([_a-z0-9\-]+)(\.[_a-z0-9\-]+)*@([a-z0-9\-]{2,}\.)*([a-z]{2,}))*$')
         if not pattern.match(field.data.replace(" ", "")):
             raise validators.ValidationError(self.message)