diff --git a/Mail/Views/Thread/WebView.swift b/Mail/Views/Thread/WebView.swift
index 5af7b89e1..a9d4a6d18 100644
--- a/Mail/Views/Thread/WebView.swift
+++ b/Mail/Views/Thread/WebView.swift
@@ -38,7 +38,7 @@ final class WebViewController: UIViewController {
             .debounce(for: .seconds(0.3), scheduler: DispatchQueue.main)
             .sink { newWidth in
                 Task {
-                    _ = try await self.model.webView.evaluateJavaScript("normalizeMessageWidth(\(newWidth), '\(self.messageUid ?? "")')")
+                    try await self.normalizeMessageWidth(webViewWidth: CGFloat(newWidth))
                 }
             }
     }
@@ -65,6 +65,10 @@ final class WebViewController: UIViewController {
         }
         #endif
     }
+
+    private func normalizeMessageWidth(webViewWidth width: CGFloat) async throws {
+        _ = try await model.webView.evaluateJavaScript("normalizeMessageWidth(\(width), '\(messageUid ?? "")')")
+    }
 }
 
 extension WebViewController: WKNavigationDelegate {
@@ -82,7 +86,7 @@ extension WebViewController: WKNavigationDelegate {
             guard readyState == "complete" else { return }
 
             _ = try await webView.evaluateJavaScript("removeAllProperties()")
-            _ = try await webView.evaluateJavaScript("normalizeMessageWidth(\(webView.frame.width), '\(messageUid ?? "")')")
+            try await normalizeMessageWidth(webViewWidth: webView.frame.width)
         }
     }
 
diff --git a/MailResources/js/mungeEmail.js b/MailResources/js/mungeEmail.js
index 3ca4eb139..abf6ed507 100644
--- a/MailResources/js/mungeEmail.js
+++ b/MailResources/js/mungeEmail.js
@@ -21,7 +21,8 @@ const PREFERENCES = {
     normalizeMessageWidths: true,
     mungeImages: true,
     mungeTables: true,
-    minimumEffectiveRatio: 0.7
+    minimumEffectiveRatio: 0.7,
+    undoPreviousChanges: true
 };
 
 let actionsLog = {};
@@ -55,15 +56,16 @@ function normalizeElementWidths(elements, webViewWidth, messageUid) {
     const documentWidth = document.body.offsetWidth;
     logInfo(`Starts to normalize elements. Document width: ${documentWidth}. WebView width: ${webViewWidth}.`);
 
-    let currentActionsLog = actionsLog[messageUid];
-    if (currentActionsLog != undefined && currentActionsLog.length > 0) {
-        logInfo('We need to undo previous changes.');
-        undoActions(currentActionsLog);
-    }
-
     for (const element of elements) {
         logInfo(`Current element: ${elementDebugName(element)}.`);
 
+        // If the script has already been run, we can undo the changes we've made and start again from scratch
+        let currentActionsLog = getActionsLog(element, messageUid);
+        if (PREFERENCES.undoPreviousChanges && currentActionsLog.length > 0) {
+            logInfo('We need to undo changes from a previous run.');
+            undoActions(currentActionsLog);
+        }
+
         // Reset any existing normalization
         const originalZoom = element.style.zoom;
         if (originalZoom) {
@@ -106,8 +108,7 @@ function transformContent(element, documentWidth, elementWidth, messageUid) {
     let newWidth = elementWidth;
     let isTransformationDone = false;
     /** Format of entries : { function: fn, object: object, arguments: [list of arguments] } */
-    actionsLog[messageUid] = [];
-    let currentActionsLog = actionsLog[messageUid];
+    let currentActionsLog = getActionsLog(element, messageUid);
 
     // Try munging all divs or textareas with inline styles where the width
     // is wider than `documentWidth`, and change it to be a max-width.
@@ -319,6 +320,20 @@ function shouldMungeTable(table) {
     return table.hasAttribute('width') || table.style.width;
 }
 
+/**
+ * Get the actionsLog associated with the element to be modified
+ * @param element Element to be modified
+ * @param messageUid MessageUid associated to the element
+ * @returns {string} Id of the actionsLog
+ */
+function getActionsLog(element, messageUid) {
+    const id= `${element.id}${messageUid}`;
+    if (actionsLog[id] === undefined) {
+        actionsLog[id] = [];
+    }
+    return actionsLog[id];
+}
+
 // Logger
 
 function logInfo(text) {