diff --git a/src/frontend/app/indexation/indexing-form/indexing-form.component.ts b/src/frontend/app/indexation/indexing-form/indexing-form.component.ts
index e76589c813c1523537292c44e3f0e186d64246ee..9a012e9e765cd43ba62a3feba6175683a6d402be 100755
--- a/src/frontend/app/indexation/indexing-form/indexing-form.component.ts
+++ b/src/frontend/app/indexation/indexing-form/indexing-form.component.ts
@@ -1298,7 +1298,10 @@ export class IndexingFormComponent implements OnInit {
                     if (this.functions.empty(item.unit)) {
                         item.unit = 'mail';
                     }
-                    item.mandatory = true;
+                    if (item.identifier !== 'registeredMail_number') {
+                        item.mandatory = true;
+                    }
+
                     this.initValidator(item);
                 }
             });