Hi,
The removal policy for each DNSBL is different. Checking which DNSBL/Reputation Server your server's listed in isn't always easy since not all of them are publicly accessible.
A good place to start would be the link Zach provided. For the DNSBL in which you find your IP listed you'll have to visit each of their web sites and find their removal policy.
Remeber, they don't do a thing to your ability to send e-mail to another server. It's up to the sites that use the DNSBL to use them responsibly.
Since you mentioned HotMail, visit this URL to start:
http://mail.live.com/mail/postmaster.aspx
And I suggest to Use the following link to provide additional information and an hotmail agent will contact you via email.
https://support.microsoft.com/en-us/product/msn-explorer/msn-explorer/msn-explorer?productkey=edfsesc&mkt=en-us
Best Regards.