自从wp_mail 是可插入的，我们可以有选择地覆盖它。我在通用功能插件中运行以下代码：

/**
 * Email Async.
 * 
 * We override the wp_mail function for all non-cron requests with a function that simply
 * captures the arguments and schedules a cron event to send the email.
 */
if ( ! defined( \'DOING_CRON\' ) || ( defined( \'DOING_CRON\' ) && ! DOING_CRON ) ) {

    function wp_mail() {

        // Get the args passed to the wp_mail function
        $args = func_get_args();

        // Add a random value to work around that fact that identical events scheduled within 10 minutes of each other
        // will not work. See: http://codex.wordpress.org/Function_Reference/wp_schedule_single_event
        $args[] = mt_rand();

        // Schedule the email to be sent
        wp_schedule_single_event( time() + 5, \'cron_send_mail\', $args );
    }
}

/**
 * This function runs during cron requests to send emails previously scheduled by our
 * overrided wp_mail function. We remove the last argument because it is just a random
 * value added to make sure the cron job schedules correctly.
 * 
 * @hook    cron_send_mail  10
 */
function example_cron_send_mail() {

    $args = func_get_args();

    // Remove the random number that was added to the arguments
    array_pop( $args );

    call_user_func_array( \'wp_mail\', $args );
}

/**
 * Hook the mail sender. We accept more arguments than wp_mail currently takes just in case
 * they add more in the future.
 */
add_action( \'cron_send_mail\', \'example_cron_send_mail\', 10, 10 );