diff --git a/config/site_settings.yml b/config/site_settings.yml
index a3e32d78328..fc93ceb1947 100644
--- a/config/site_settings.yml
+++ b/config/site_settings.yml
@@ -745,7 +745,7 @@ email:
     default: "pkcs7|x-vcard"
   attachment_filename_blacklist:
     type: list
-    default: "smime.p7s|signature.asc"
+    default: "smime.p7s|signature.asc|winmail.dat"
   enable_forwarded_emails: false
   always_show_trimmed_content: false
   private_email: false