diff --git a/addons/mail/static/src/css/mail_group.css b/addons/mail/static/src/css/mail_group.css
index b700cb8c80f..9ca0055c17f 100644
--- a/addons/mail/static/src/css/mail_group.css
+++ b/addons/mail/static/src/css/mail_group.css
@@ -48,10 +48,11 @@
   -o-border-radius: 3px;
   -ms-border-radius: 3px;
   border-radius: 3px;
+  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 rgba(0, 0, 0, 0.4);
   -o-box-shadow: 0 1px 4px rgba(0, 0, 0, 0.4);
-  -box-shadow: 0 1px 4px rgba(0, 0, 0, 0.4);
 }
 
 .oe_group_photo {