diff --git a/addons/mail/static/src/less/thread.less b/addons/mail/static/src/less/thread.less
index 03bb984599a..f18643dde41 100644
--- a/addons/mail/static/src/less/thread.less
+++ b/addons/mail/static/src/less/thread.less
@@ -104,6 +104,10 @@
             max-width: 100%;
             word-wrap: break-word;
 
+            &.o_mail_note {
+                background-color: @odoo-color-silver-dark;
+            }
+
             .o_mail_subject {
                 font-style: italic;
             }