diff --git a/CHANGELOG b/CHANGELOG
index 2eafe598b..676680bfe 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -48,6 +48,7 @@ CHANGELOG Roundcube Webmail
 - Use contact_search_name format in popup on results in compose contacts search
 - Fix handling of 'mailto' and 'error' arguments in message_before_send hook (#5347)
 - Fix missing localization of HTML editor when assets_dir != INSTALL_PATH
+- Fix handling of blockquote tags with mixed case on html2text conversion (#5363)
 
 RELEASE 1.2.0
 -------------
diff --git a/program/lib/Roundcube/rcube_html2text.php b/program/lib/Roundcube/rcube_html2text.php
index 2c16171b5..0639edd84 100644
--- a/program/lib/Roundcube/rcube_html2text.php
+++ b/program/lib/Roundcube/rcube_html2text.php
@@ -587,11 +587,11 @@ class rcube_html2text
     {
         $level = 0;
         $offset = 0;
-        while (($start = strpos($text, '<blockquote', $offset)) !== false) {
+        while (($start = stripos($text, '<blockquote', $offset)) !== false) {
             $offset = $start + 12;
             do {
-                $end = strpos($text, '</blockquote>', $offset);
-                $next = strpos($text, '<blockquote', $offset);
+                $end = stripos($text, '</blockquote>', $offset);
+                $next = stripos($text, '<blockquote', $offset);
 
                 // nested <blockquote>, skip
                 if ($next !== false && $next < $end) {
diff --git a/tests/Framework/Html2text.php b/tests/Framework/Html2text.php
index be1488295..889ba8241 100644
--- a/tests/Framework/Html2text.php
+++ b/tests/Framework/Html2text.php
@@ -79,7 +79,7 @@ class rc_html2text extends PHPUnit_Framework_TestCase
     {
         $html = <<<EOF
 <br>Begin<br><blockquote>OUTER BEGIN<blockquote>INNER 1<br></blockquote><div><br></div><div>Par 1</div>
-<blockquote>INNER 2</blockquote><div><br></div><div>Par 2</div>
+<blockQuote>INNER 2</blockquote><div><br></div><div>Par 2</div>
 <div><br></div><div>Par 3</div><div><br></div>
 <blockquote>INNER 3</blockquote>OUTER END</blockquote>
 EOF;