Where can I find best pratice to not getting black listed

I have been using PHP list for over 8 years and had a problem with my general emails not getting to me so I decided to get a hosting package so I would have another domain (ip) and email that would catch the negative reputation. I did that, and it worked good for a while but now this new hosting company has blocked all out going emails. I have been sending less than 90 an hour and play by all the rules about unsubscribing and all. Any ideas what would be a good course of action?