wpml_switch_language_for_email

$all_users = get_users();

foreach( $all_users as $user ) {
	// Switch language to user language.
	do_action('wpml_switch_language_for_email', $user->user_email );

	$subject = __('Hello, World!', 'text-domain');
	$message = __('This is our newsletter', 'text-domain');

	wp_mail( $user->user_email, $subject, $message);

	// Switch language back.
	do_action('wpml_restore_language_from_email');
}