Hi Kylie,
If this email address has been blacklisted then it's up to the owner of that mailbox to contact the owner of the 'blacklist' it's on and ask them to be removed.
A domain or server is generally placed on a blacklist because there has been some undesirable activity happening in relation to that server or domain. Most servers or domains are listed as a result of directly sending spam or viruses to special detectors (spamtraps) or by initiating SMTP transactions that look similar to viruses or botnet-proxies.