MailChimp allows you to buy credits as you go, or pay them monthly by subscriber count. It's also built for marketers so after importing your list there your ma

MailChimp allows you to buy credits as you go, or pay them monthly by subscriber count. It's also built for marketers so after importing your list there your marketing guy should be fine. If you're looking to do it cheaper, SendGrid offers a newsletter function that's less easy to use and has less features but will allow you to do it cheaper.