Hotmail and IP in blacklist - how to solve now?

Hotmail, which is operated under now, is provided by Microsoft. You can request they remove your IP address by completing the form here (this may require signing up for first).

It will take a few days for them to investigate the report, and if your IP address was not associated with sending Spam, you'll receive an email back from their support team. It will then take another 24-48 hours for the IP address to be fully unblocked in their system.

You should also test your IP address in a multi-RBL check site like this one. Visit each site that your IP address is listed in and test it there to see what message they relay back. If there's something you can address, then do so and request that they remove your IP address from their list.

It may also be wise to setup and configure SPF and PTR records in the DNS for your mail server, as well as DomainKeys Identified Mail.