@cartero, were you on a dedicated server? I can't imagine any host in their right mind permitting this kind of server load on shared server space.
Personally, I've got three sites running WP on DH and although I don't send out bulk email, I've been very happy with their plans and their pricing.
I also highly recommend Textdrive (http://textdrive.com), and have two WP sites running there with no problems. I was lucky enough to get in on one of their VC campaigns. Otherwise, they are somewhat pricey, but well worth it in terms of service, security and customer support. Textdrive supports open source projects and even donates 10% of your hosting fee to the open source project of your choice (e.g., TextPattern, WordPress). That's a nice gesture, I believe.