If you receive a bounced-back message saying that IP address X.X.X.X is blacklisted by a spam organisation this means that the mentioned IP address has been blacklisted for sending unsolicited mail. Such a listing is caused by a complaint to the spam-fighting organisation.
In the bounced-back mail there will be a link for more information and what you can do in this case. If you recognize the reported ip as your local one please read further on how to remove it.
On the other hand if you find this is our server's shared ip you don't have to take any actions. We would have been already informed about this issue and taken all necessary actions to remove it from the list.
It might take around 24-48 hours for the removal to be confirmed and you will be able to send your mail without problems.