If you get blacklisted it can be a huge pain, but is possible to get your ip off the list if you go through the proper channels. The best place to find out of you have been blacklisted is at.
If you emails meet all the criteria as specified in the regulation, you must contact a blacklist owner, such as SpamCop, and explain your problem. The blacklisting agency will require you to send them copies of the emails not being delivered to establish if you are following regulatory guidelines.
Getting “whitelisted”, with the major ISPs, is the best way to not get blacklisted. The “big four” ISPs, AOL, Yahoo, Google Mail, and MSN (Hotmail), take an aggressive stance against spamming and those who do it. However if you wish to get whitelisted with them you need to apply to each one seporately. Below are the direct links to get whitelisted for the big four.