diff -urN ../z-push-2.6.2+0.orig/src/include/mimeDecode.php ./src/include/mimeDecode.php
--- ../z-push-2.6.2+0.orig/src/include/mimeDecode.php	2023-03-18 01:57:07.838734000 +0200
+++ ./src/include/mimeDecode.php	2023-06-11 21:13:40.017219000 +0300
@@ -874,8 +874,14 @@
                 break;
         }
 
-        if ($detectCharset && strtolower($charset) != $this->_charset) {
-            if (@mb_check_encoding($input, $charset) == false) {
+        if ($detectCharset && $charset && strtolower($charset) != $this->_charset) {
+            $encoding_valid = true;
+            try {
+                mb_check_encoding("", $charset);
+            } catch (Throwable $e) {
+                $encoding_valid = false;
+            }
+            if (!$encoding_valid or (@mb_check_encoding($input, $charset) == false)) {
                 // list of encodings, sorted by priority to assist mb_detect_encoding()
                 $encodingPriority = array('UTF-8', 'SJIS', 'GB18030', 'ISO-8859-1', 'ISO-8859-2', 'ISO-8859-3', 'ISO-8859-4',
                     'ISO-8859-5', 'ISO-8859-6', 'ISO-8859-7', 'ISO-8859-8', 'ISO-8859-9', 'ISO-8859-10', 'ISO-8859-13',