diff --git a/dashboard/src/components/MailboxDialog.vue b/dashboard/src/components/MailboxDialog.vue
index 0e9dea53b..c1034f7cf 100644
--- a/dashboard/src/components/MailboxDialog.vue
+++ b/dashboard/src/components/MailboxDialog.vue
@@ -84,7 +84,7 @@ defineExpose({
     mailbox.value = m;
 
     name.value = m ? m.name : '';
-    domain.value = m ? m.domain : '';
+    domain.value = m ? m.domain : props.domains[0].domain;
     ownerId.value = m ? m.ownerId : '';
     aliases.value = m ? JSON.parse(JSON.stringify(m.aliases)) : [];
     active.value = m ? m.active : true;