You'll want to remove your domain from blacklists as soon as possible because they're often shared between providers. If you believe you've fixed the root cause of the listing, by ensuring spam isn't being sent, head to the blacklist providers site and follow their blacklist-removal process.
You may find two types of removal process:
Self-Service Removal – This means that you can remove the blacklist manually without much trouble or waiting. You must ensure you have fixed the issues before doing this. If the domain is listed again it may be more difficult to remove.
Time-Based Removal – Most blacklists have a time-based process whereby domains that have lower-level listings will be removed on a periodic basis, usually 1-2 weeks. Higher-level listings may take a longer period of time to be removed.