diff --git a/addons/mass_mailing/static/src/scss/themes/theme_default.scss b/addons/mass_mailing/static/src/scss/themes/theme_default.scss
index 44badb7aa08..34700e20d7a 100644
--- a/addons/mass_mailing/static/src/scss/themes/theme_default.scss
+++ b/addons/mass_mailing/static/src/scss/themes/theme_default.scss
@@ -126,6 +126,35 @@ div.col:not([align]) {
             }
         }
     }
+    // Background Images
+    .oe_img_bg {
+        background-size: cover;
+        background-repeat: no-repeat;
+
+        &.o_bg_img_opt_repeat {
+            background-size: auto;
+            background-repeat: repeat;
+        }
+        &.o_bg_img_center {
+            background-position: center;
+        }
+
+        // Compatibility <= 13.0, TODO remove?
+        // -----------------------------------
+        &.o_bg_img_opt_contain {
+            background-size: contain;
+            background-position: center center;
+        }
+        &.o_bg_img_opt_custom {
+            background-size: auto;
+        }
+        &.o_bg_img_opt_repeat_x {
+            background-repeat: repeat-x;
+        }
+        &.o_bg_img_opt_repeat_y {
+            background-repeat: repeat-y;
+        }
+    }
 }
 
 // ===== Snippets (specific) =====