diff --git a/app/src/main/java/eu/faircode/email/BoundaryCallbackMessages.java b/app/src/main/java/eu/faircode/email/BoundaryCallbackMessages.java
index 7a1905818a..59a5729949 100644
--- a/app/src/main/java/eu/faircode/email/BoundaryCallbackMessages.java
+++ b/app/src/main/java/eu/faircode/email/BoundaryCallbackMessages.java
@@ -733,7 +733,7 @@ public class BoundaryCallbackMessages extends PagedList.BoundaryCallback<TupleMe
                             .replace("ij", "ij");
                     search = Normalizer
                             .normalize(search, Normalizer.Form.NFKD)
-                            .replaceAll("[^\\p{ASCII}]", "");
+                            .replaceAll("[^\\p{ASCII}]", "?");
                 }
 
                 List<String> word = new ArrayList<>();