diff --git a/src/collective/volto/formsupport/restapi/services/submit_form/post.py b/src/collective/volto/formsupport/restapi/services/submit_form/post.py
index 62edd3a..a03b1b6 100644
--- a/src/collective/volto/formsupport/restapi/services/submit_form/post.py
+++ b/src/collective/volto/formsupport/restapi/services/submit_form/post.py
@@ -314,7 +314,8 @@ def get_subject(self):
         )
 
         for i in self.form_data.get("data", []):
-            field_id = i.get("field_id")
+            # Handle `field_name_321323` kind of id used by frontend package
+            field_id = i.get("field_id", "").split("_")[-1]
 
             if not field_id:
                 continue