diff --git a/addons/mail/static/src/css/mail_group.css b/addons/mail/static/src/css/mail_group.css
index 467bc53d80f..c1cefee9070 100644
--- a/addons/mail/static/src/css/mail_group.css
+++ b/addons/mail/static/src/css/mail_group.css
@@ -52,7 +52,7 @@
   border-collapse: separate;
   -moz-box-shadow: 0 1px 4px rgba(0, 0, 0, 0.4);
   -webkit-box-shadow: 0 1px 4px rgba(0, 0, 0, 0.4);
-  box-shadow: 0 1px 4px 3px rgba(0, 0, 0, 0.4);
+  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.4);
   -o-box-shadow: 0 1px 4px rgba(0, 0, 0, 0.4);
 }