Changelog entry for previous commit and change default charset for the Email library to whatever the config array says
diff --git a/system/core/Utf8.php b/system/core/Utf8.php
index 9e6a4eb..1ff0298 100644
--- a/system/core/Utf8.php
+++ b/system/core/Utf8.php
@@ -136,7 +136,7 @@
 		{
 			return @iconv($encoding, 'UTF-8', $str);
 		}
-		elseif (function_exists('mb_convert_encoding'))
+		elseif (MB_ENABLED === TRUE)
 		{
 			return @mb_convert_encoding($str, 'UTF-8', $encoding);
 		}