Also affects on 1.9.4.1+
SUPEE-11219 adds a new method linkFilter in app/code/core/Core/Model/Input/Filter/MaliciousCode.php that uses DOMDocument load and save, after it loses Russian symbols.
Cyrillic (Russian) symbols lost on fly during preview Email Newsletter, didn't test affect on sending.
How to solve:
Just add
$html = mb_convert_encoding($html, 'HTML-ENTITIES', 'UTF-8');
before
if (!$dom->loadHTML($html)) {
