diff --git a/FAQ.md b/FAQ.md
index 18755d8f78..f697c34ebb 100644
--- a/FAQ.md
+++ b/FAQ.md
@@ -2681,6 +2681,7 @@ You can enable downloading message headers in the connection settings and check
 
 Some common header conditions (regex):
 
+* *.&ast;To:.&ast;undisclosed-recipients.&ast;*
 * *.&ast;Auto-Submitted:.&ast;* [RFC3834](https://tools.ietf.org/html/rfc3834)
 * *.&ast;List-Unsubscribe:.&ast;* [RFC3834](https://datatracker.ietf.org/doc/html/rfc2369)
 * *.&ast;Content-Type:.&ast;multipart/report.&ast;* [RFC3462](https://tools.ietf.org/html/rfc3462)