diff --git a/core/lib/presentation/utils/html_transformer/base/dom_transformer.dart b/core/lib/presentation/utils/html_transformer/base/dom_transformer.dart
index e6d437af2..503633121 100644
--- a/core/lib/presentation/utils/html_transformer/base/dom_transformer.dart
+++ b/core/lib/presentation/utils/html_transformer/base/dom_transformer.dart
@@ -27,7 +27,7 @@ abstract class DomTransformer {
 
   Tuple2<String, String>? findImageUrlFromStyleTag(String style) {
     try {
-      final regExp = RegExp(r'background-image:\s*url\(([^)]+)\).*?');
+      final regExp = RegExp(r'''\bbackground-image\s*:\s*url\(\s*['"]?([^' ")]+)['"]?\s*\)''');
       final match = regExp.firstMatch(style);
       if (match == null) {
         return null;
diff --git a/core/lib/presentation/utils/html_transformer/dom/normalize_line_height_in_style_transformer.dart b/core/lib/presentation/utils/html_transformer/dom/normalize_line_height_in_style_transformer.dart
index 07119143c..6bf21bae2 100644
--- a/core/lib/presentation/utils/html_transformer/dom/normalize_line_height_in_style_transformer.dart
+++ b/core/lib/presentation/utils/html_transformer/dom/normalize_line_height_in_style_transformer.dart
@@ -15,8 +15,9 @@ class NormalizeLineHeightInStyleTransformer extends DomTransformer {
     Map<String, String>? mapUrlDownloadCID,
   }) async {
     try {
+      final alternation = _removableLineHeights.map(RegExp.escape).join('|');
       final pattern = RegExp(
-        r'line-height\s*:\s*(?:' + _removableLineHeights.join('|') + r')\s*;?',
+        r'line-height\s*:\s*(?:' + alternation + r')\s*;?',
         caseSensitive: false,
       );
 
@@ -29,7 +30,7 @@ class NormalizeLineHeightInStyleTransformer extends DomTransformer {
         var updatedStyle = originalStyle.replaceAll(pattern, '').trim();
 
         // Remove extra spaces (>=2 spaces → 1 space)
-        updatedStyle = updatedStyle.replaceAll(RegExp(r'\s{2,}'), ' ');
+        updatedStyle = updatedStyle.replaceAll(RegExp(r' {2,}'), ' ');
 
         if (updatedStyle != originalStyle) {
           if (updatedStyle.isEmpty) {
diff --git a/core/lib/utils/html/html_utils.dart b/core/lib/utils/html/html_utils.dart
index c87a23135..f232d87d3 100644
--- a/core/lib/utils/html/html_utils.dart
+++ b/core/lib/utils/html/html_utils.dart
@@ -700,8 +700,8 @@ class HtmlUtils {
   }
 
   static String addQuoteToggle(String htmlString) {
-    final likelyHtml = htmlString.contains(RegExp(r'<[a-zA-Z][^>]*>')) && // Contains a start tag
-      htmlString.contains(RegExp(r'</[a-zA-Z][^>]*>')); // Contains an end tag
+    final likelyHtml = htmlString.contains(RegExp(r'<[a-zA-Z][^>\s]*[^>]*>')) && // Contains a start tag
+      htmlString.contains(RegExp(r'</[a-zA-Z][^>]{0,128}>')); // Contains an end tag
 
     if (!likelyHtml) {
       return htmlString; // Not likely HTML, return original
@@ -850,8 +850,9 @@ class HtmlUtils {
     } while (decoded != cleaned && iterations < maxIterations);
 
     // Delete all remaining HTML tags → replace tag with space to avoid text sticking
+    final String tagsPipe = validTags.map(RegExp.escape).join('|');
     final tagRegex = RegExp(
-      '</?(${validTags.join('|')})(\\s+[^>]*)?>',
+      '</?(?:$tagsPipe)(?:\\s+[^>]*)?>',
       caseSensitive: false,
     );
     cleaned = cleaned.replaceAll(tagRegex, ' ');
@@ -870,10 +871,9 @@ class HtmlUtils {
       if (container == null) return htmlString;
 
       final urlRegex = RegExp(
-        r'''(?:(?:https?:\/\/)|(?:ftp:\/\/)|(?:mailto:)|(?:file:\/\/)|(?:www\.))(?!\.)(?!.*\.\.)([^\s<]+[^<.,:;\"\'\)\]\s!?])''',
+        r'''(?:https?://|ftp://|mailto:|file://|www\.)[^\s<.]+(?:\.[^\s<.]+)*(?<![.,:;!?"')\]])''',
         caseSensitive: false,
         multiLine: true,
-        dotAll: true,
       );
 
       _processNode(container, urlRegex);
@@ -899,6 +899,9 @@ class HtmlUtils {
   };
 
   static void _processNode(dom.Node node, RegExp urlRegex) {
+    // 1. Anchored with ^ to fail instantly if the start doesn't match
+    // 2. Grouped for clarity
+    final protocolRegex = RegExp(r'^(?:https?|ftp|mailto|file)');
     for (var child in node.nodes.toList()) {
       // Skip if node or parent node is in tag to skip
       final parentTag = child.parent?.localName;
@@ -929,7 +932,7 @@ class HtmlUtils {
             nodes.add(dom.Text(url));
           } else {
             // Normalize href
-            final href = url.startsWith(RegExp(r'https?|ftp|mailto|file'))
+            final href = url.startsWith(protocolRegex)
                 ? url
                 : 'https://$url';
 
diff --git a/core/lib/utils/string_convert.dart b/core/lib/utils/string_convert.dart
index f8021f027..e1ebb646e 100644
--- a/core/lib/utils/string_convert.dart
+++ b/core/lib/utils/string_convert.dart
@@ -9,7 +9,8 @@ import 'package:html/parser.dart';
 import 'package:http_parser/http_parser.dart';
 
 class StringConvert {
-  static const String emailSeparatorPattern = r'[ ,;]+';
+  // Change the pattern to include newlines directly to avoid the .replaceAll() step
+  static const String emailSeparatorPattern = r'[ ,;\n\r\t]+';
 
   static String? writeEmptyToNull(String text) {
     if (text.isEmpty) return null;
@@ -31,25 +32,28 @@ class StringConvert {
 
   static List<String> extractStrings(String input, String separatorPattern) {
     try {
-      // Check if the input is URL encoded
+      // 1. URL Decoding
       if (input.contains('%')) {
-        input = Uri.decodeComponent(input); // Decode URL encoding
+        input = Uri.decodeComponent(input);
       }
 
-      // Efficient Base64 validation: Check length and minimal regex match
-      if (input.length % 4 == 0 && input.contains(RegExp(r'^[A-Za-z0-9+/=]+$'))) {
-        try {
-          input = utf8.decode(base64.decode(input)); // Decode Base64 encoding
-        } catch (_) {
-          // Ignore if decoding fails
+      // 2. Base64 Check - Using a non-regex check first is faster
+      if (input.length % 4 == 0 && !input.contains(' ')) {
+        // Only run regex if basic length/whitespace checks pass
+        if (RegExp(r'^[A-Za-z0-9+/=]+$').hasMatch(input)) {
+          try {
+            input = utf8.decode(base64.decode(input));
+          } catch (_) {
+            // Ignore if decoding fails
+          }
         }
       }
 
+      // 3. Optimized Split
+      // We use the pattern directly and skip the redundant .replaceAll() and .trim()
       final RegExp separator = RegExp(separatorPattern);
       final listStrings = input
-          .replaceAll('\n', ' ')
           .split(separator)
-          .map((value) => value.trim())
           .where((value) => value.isNotEmpty)
           .toList();
       log('StringConvert::extractStrings:listStrings = $listStrings');
@@ -128,16 +132,32 @@ class StringConvert {
         text.split('\n').where((line) => line.trim().isNotEmpty).toList();
     if (lines.length < 2) return false;
 
-    // Check for Markdown table
-    final mdSeparatorRegex = RegExp(r'^\|?(\s*:?-+:?\s*\|)+(\s*:?-+:?\s*)\|?$');
-    final isMarkdown = lines.any((line) => mdSeparatorRegex.hasMatch(line));
+    // 1. Hardened Markdown Separator Regex
+    // We use [ \t]* instead of \s to be specific and avoid newline issues
+    // We ensure the dash sequence is clearly delimited
+    final mdSeparatorRegex = RegExp(
+        r'^\|?(?:[ \t]*:?-+:?[ \t]*\|)+[ \t]*:?-+:?[ \t]*\|?$',
+        multiLine: false);
 
-    // Check for ASCII art table (with borders made of +, -, |, /, \, =)
-    final asciiArtRegex = RegExp(r'[\+\-\|/\\=]');
-    final isAsciiArt = lines.every((line) =>
-        line.contains(asciiArtRegex) && line.split(asciiArtRegex).length > 1);
-    log('StringConvert::isTextTable:isMarkdown = $isMarkdown | isAscii = $isAsciiArt');
-    return isMarkdown || isAsciiArt;
+    // 2. Optimized ASCII Check
+    // We use hasMatch instead of split().length for better performance
+    final asciiArtRegex = RegExp(r'[+\-|/\\=]');
+
+    bool isMarkdown = false;
+    bool allLinesHaveAscii = true;
+
+    for (final line in lines) {
+      if (!isMarkdown && mdSeparatorRegex.hasMatch(line)) {
+        isMarkdown = true;
+      }
+      if (allLinesHaveAscii && !asciiArtRegex.hasMatch(line)) {
+        allLinesHaveAscii = false;
+      }
+      // Early exit if we found a table but also know it's not ASCII art
+      if (isMarkdown && !allLinesHaveAscii) break;
+    }
+
+    return isMarkdown || (allLinesHaveAscii && lines.length >= 2);
   }
 
   static List<NamedAddress> extractNamedAddresses(String input) {
@@ -156,12 +176,11 @@ class StringConvert {
       input = input.replaceAll('\n', ' ');
       final results = <NamedAddress>[];
 
-      final pattern = RegExp(r'''(?:"([^"]+)"|'([^']+)'|)\s*<([^>]+)>''');
+      final pattern = RegExp(r'''(?:(?:"([^"]+)"|'([^']+)')\s*)?<([^>]+)>''');
 
       int currentIndex = 0;
-      final matches = pattern.allMatches(input).toList();
-
-      for (final match in matches) {
+      // Use a for-in loop directly on the iterable to save memory
+      for (final match in pattern.allMatches(input)) {
         if (match.start > currentIndex) {
           final between = input.substring(currentIndex, match.start);
           results.addAll(_splitPlainAddresses(between, emailSeparatorPattern));
diff --git a/lib/main/utils/app_utils.dart b/lib/main/utils/app_utils.dart
index 2194a8eed..f082b060b 100644
--- a/lib/main/utils/app_utils.dart
+++ b/lib/main/utils/app_utils.dart
@@ -54,7 +54,7 @@ class AppUtils {
   static bool isEmailLocalhost(String email) {
     final normalized = email.trim();
     return RegExp(
-        r'^(([^<>()[\]\\.,;:\s@"]+(\.[^<>()[\]\\.,;:\s@"]+)*)|(".+"))@localhost$'
+        r'^(?:"[^"\r\n]+"|[^<>()[\]\\.,;:\s@"]+(?:\.[^<>()[\]\\.,;:\s@"]+)*)@localhost$'
     ).hasMatch(normalized);
   }