diff --git a/src/lib/utils/utils.php b/src/lib/utils/utils.php
index e6826f75..d4b5d8e1 100644
--- a/src/lib/utils/utils.php
+++ b/src/lib/utils/utils.php
@@ -1278,7 +1278,11 @@ private static function convertRawHeader2Utf8($nonencstr, $utf8str) {
                 $str .= $val->text;
             }
             else {
-                $str .= @mb_convert_encoding($val->text, "utf-8", $val->charset);
+                try {
+                    $str .= @mb_convert_encoding($val->text, "utf-8", $val->charset);
+                } catch (ValueError $exception) {
+                    $str .= @iconv($val->charset, "utf-8", $val->text);
+                }
             }
         }
         if (!$isiso2022jp) {