in include/unicode.inc, the mime_header_encode function, replaced
$chunk_size = 47; // floor((75 - strlen("=?UTF-8?B??=")) * 0.75);with
$chunk_size = 400; // floor((75 - strlen("=?UTF-8?B??=")) * 0.75);Its an overly big chunk size, since the mail form does not allow lengthy subjects, however, utf-8 encoding seems to lengthen things a low...
Now - mail passes through just fine - no linebreaks in the subject (who came up with that idea anyway) - and no lost messages.