I have a wordpress site with user base of around 4500. I want to send out email notifications for site updates, new posts etc etc. I am using wordpress private email plugin - but it takes long time to send those out. Also I am wondering if that puts huge load on server and my host may have issues if keep mass mailing like this. Is this real? Are there any good solutions where I can easily import all user emails and send out emails without causing lot of trouble. Thanks in advance