Here is my code which help me resolve problems with sending emails from admin translated, when rest is in english.
function redefine_locale($locale) {
global $l10n;
unset($l10n['YOUR_DOMAIN']);
add_filter('locale', $f=create_function('', "return '{$locale}';"));
load_plugin_textdomain('YOUR_DOMAIN', FALSE, dirname(plugin_basename(__FILE__)));
remove_filter('locale', $f);
}
Usage:
function send_mail() {
PolcodeWpsc_Utils::redefine_locale(get_option('WPLANG'));
$message = __('lorem ipsum', 'YOUR_DOMAIN');
wp_mail();
PolcodeWpsc_Utils::redefine_locale(get_locale());
}