diff --git a/js/mzta-utils.js b/js/mzta-utils.js
index d7f1b300..d10e309d 100644
--- a/js/mzta-utils.js
+++ b/js/mzta-utils.js
@@ -203,17 +203,21 @@ export async function createTag(tag) {
   if(prefs_tag.add_tags_first_uppercase) tag = tag.toLowerCase().charAt(0).toUpperCase() + tag.toLowerCase().slice(1);
   try {
     if(await isThunderbird128OrGreater()) {
-      return browser.messages.tags.create('ta-'+tag.toLowerCase(), tag, generateHexColorForTag());
+      return browser.messages.tags.create('$ta-'+sanitizeString(tag), tag, generateHexColorForTag());
     }else{
-      return browser.messages.createTag('ta-'+tag.toLowerCase(), tag, generateHexColorForTag());
+      return browser.messages.createTag('$ta-'+sanitizeString(tag), tag, generateHexColorForTag());
     }
   } catch (error) {
     console.error('[ThunderAI] Error creating tag:', error);
   }
 }
 
+export function checkIfTagExists(tag, tags_list) {
+  return tags_list.hasOwnProperty("$ta-" + sanitizeString(tag)); 
+}
+
 export async function assignTagsToMessage(messageId, tags) {
-  tags = tags.map(tag => `ta-${tag.toLowerCase()}`);
+  tags = tags.map(tag => `$ta-${sanitizeString(tag)}`);
   let msg_prop = await browser.messages.get(messageId);
   tags = tags.concat(msg_prop.tags || []);
   try {
@@ -223,6 +227,22 @@ export async function assignTagsToMessage(messageId, tags) {
   }
 }
 
+function sanitizeString(input) {
+  input = input.toLowerCase();
+  // Define the regex to match valid characters
+  const regex = /^[^ ()/{%*<>"]+$/;
+  // Filter out invalid characters from the string
+  let sanitized = '';
+  for (const char of input) {
+    // Check if the character is valid according to the regex
+    if (regex.test(char)) {
+      sanitized += char;
+    }
+  }
+
+  return sanitized;
+}
+
 function generateHexColorForTag() {
   const red = Math.floor(Math.random() * 256);
   const green = Math.floor(Math.random() * 256);
diff --git a/mzta-background.js b/mzta-background.js
index 8aca3e94..2ad8cd15 100644
--- a/mzta-background.js
+++ b/mzta-background.js
@@ -20,7 +20,7 @@ import { mzta_script } from './js/mzta-chatgpt.js';
 import { prefs_default } from './options/mzta-options-default.js';
 import { mzta_Menus } from './js/mzta-menus.js';
 import { taLogger } from './js/mzta-logger.js';
-import { getCurrentIdentity, getOriginalBody, replaceBody, setBody, i18nConditionalGet, generateCallID, migrateCustomPromptsStorage, migrateDefaultPromptsPropStorage, getGPTWebModelString, getTagsList, createTag, assignTagsToMessage } from './js/mzta-utils.js';
+import { getCurrentIdentity, getOriginalBody, replaceBody, setBody, i18nConditionalGet, generateCallID, migrateCustomPromptsStorage, migrateDefaultPromptsPropStorage, getGPTWebModelString, getTagsList, createTag, assignTagsToMessage, checkIfTagExists } from './js/mzta-utils.js';
 
 await migrateCustomPromptsStorage();
 await migrateDefaultPromptsPropStorage();
@@ -241,7 +241,7 @@ messenger.runtime.onMessage.addListener((message, sender, sendResponse) => {
                     let new_tags = [];
                     for (const tag of message.tags) {
                         console.log(">>>>>>>>>>>>>>> tag: " + tag);
-                        if (!all_tags_list.hasOwnProperty("ta-" + tag.toLowerCase())) {
+                        if (!checkIfTagExists(tag, all_tags_list)) {
                             taLog.log("Creating tag: " + tag);
                             await createTag(tag);
                         }