1 files changed, 1 insertions, 0 deletions
diff --git a/addons/mass_mailing/static/src/less/themes/theme_default.less b/addons/mass_mailing/static/src/less/themes/theme_default.less
index cfd1264e0c7..adfa4bba5ce 100644
--- a/addons/mass_mailing/static/src/less/themes/theme_default.less
+++ b/addons/mass_mailing/static/src/less/themes/theme_default.less
@@ -50,6 +50,7 @@
 // ===== Layout =====
 .o_layout {
     overflow: hidden;
+    box-sizing: content-box;
     width: 94%;
     min-height: 100%;
     background-color: @o_mm_def_color_alpha;