diff --git a/addons/mass_mailing/static/src/js/mailing_mailing_view_form_full_width.js b/addons/mass_mailing/static/src/js/mailing_mailing_view_form_full_width.js
index bfbb55e8ddf..e9c98b8d570 100644
--- a/addons/mass_mailing/static/src/js/mailing_mailing_view_form_full_width.js
+++ b/addons/mass_mailing/static/src/js/mailing_mailing_view_form_full_width.js
@@ -108,7 +108,11 @@ const MassMailingFullWidthFormController = FormController.extend({
         } else {
             const ref = $iframeDoc.find('#iframe_target')[0];
             if (ref) {
-                this.$iframe.height(Math.max(ref.scrollHeight + VERTICAL_OFFSET, minHeight));
+                this.$iframe.css({
+                    height: this._isFullScreen()
+                        ? $(window).height()
+                        : Math.max(ref.scrollHeight + VERTICAL_OFFSET, minHeight),
+                });
             }
         }
     },
@@ -126,7 +130,6 @@ const MassMailingFullWidthFormController = FormController.extend({
         const isFullscreen =  this._isFullScreen();
         if (isFullscreen) {
             $sidebar.height(windowHeight);
-            this.$iframe.height(windowHeight);
             $sidebar.css({
                 top: '',
                 bottom: '',