Secondly, go here: http://mxtoolbox.com/blacklists.aspx and add your IP address to see if it is blacklisted.
If YES - once done, click on the DETAILS button, scroll to the bottom of page and copy REASON FOR LISTING link into your browser.
IMPORTANT: Fix the reason for the listing
BEFORE delisting.
Each blacklisting service has their own reasons and ways to de-list so once you get there look around to find the De-list.
