diff --git a/django_mailbox/models.py b/django_mailbox/models.py
index 4e0c94b4..c623cdf3 100644
--- a/django_mailbox/models.py
+++ b/django_mailbox/models.py
@@ -881,7 +881,8 @@ def __getitem__(self, name):
         return value
 
     def __str__(self):
-        return self.document.url
+        return f'{self.message}: {self.document.url if self.document else None}'
+
 
     class Meta:
         verbose_name = _('Message attachment')