You need to follow the can spam laws. The best way to avoid your IP from being banned is to us a third party autoresponder system like Getresponse and Aweber. They require a double opt-in. You can still get banned even if you follow all the rules. Some people who double-opt in and want your information still may report you as spam if they simply had a bad day. You most likely will not get fined for the infractions unless you are really spamming people. You can get "unbanned" from some ISPs if you pay a fine and give them an explanation and information about your campaign. Otherwise you are SOL.