You may not use mb_encode_mimeheader() with mb_convert_encoding() to make subject as follows. It causes mojibake in several strings.
mb_encode_mimeheader( mb_convert_encoding($strMailSubj, "JIS", "EUC-JP") )
Set mb_internal_encoding() to *subject's* encoding and call mb_encode_mimeheader.
Example)
$__lang = mb_language();
$__enc = mb_internal_encoding();
mb_language("Japanese");
mb_internal_encoding( mb_detect_encoding($subject) );
#mb_internal_encoding( "EUC-JP" ); #just do when you know encoding of $subject
mail($to,
mb_encode_mimeheader($subject),
mb_convert_encoding($msg,"JIS","AUTO"),$header);
mb_internal_encoding( $__enc );
mb_language($__lang);
