diff --git a/tests/tine20/Felamimail/Frontend/JsonTest.php b/tests/tine20/Felamimail/Frontend/JsonTest.php
index 32fdd205fd..60f3d7dd54 100644
--- a/tests/tine20/Felamimail/Frontend/JsonTest.php
+++ b/tests/tine20/Felamimail/Frontend/JsonTest.php
@@ -2867,9 +2867,7 @@ public function testGetMessageFromNodeMsg()
             dirname(__FILE__) . '/../files/multipart_related_recipients.msg'
         );
 
-        // TODO make encodingCheck work again (in PHP 8.3+)
-        $encodingCheck = PHP_VERSION_ID < 80300;
-        $message = $this->_assertMessageFromNode($result[0]['id'], $encodingCheck);
+        $message = $this->_assertMessageFromNode($result[0]['id'], true);
         self::assertEquals(2, count($message['cc']));
         self::assertEquals('c.weiss@metaways.de', $message['cc'][0]['email']);
         self::assertEquals('name@example.com', $message['cc'][1]['email']);
diff --git a/tine20/Felamimail/Controller/Message.php b/tine20/Felamimail/Controller/Message.php
index a58d70d74e..c19b3d1a26 100644
--- a/tine20/Felamimail/Controller/Message.php
+++ b/tine20/Felamimail/Controller/Message.php
@@ -1502,8 +1502,8 @@ public function getMessageFromNode($nodeId, $mimeType = null): Felamimail_Model_
             }
             
             if ($message['body_content_type'] === 'text/html') {
-                $encoding = mb_detect_encoding($message['body']);
-                if (! $encoding) {
+                $encoding = mb_detect_encoding($message['body'], 'UTF-8', true);
+                if (!$encoding) {
                     $message['body'] = mb_convert_encoding($message['body'], 'UTF-8', 'ISO-8859-1');
                 }
                 $message->body = str_replace("\r", '', $message['body']);