Many vendors of Anti-Spam products like Barracuda compile their own internal list of IP's they deem a threat. If you get added to one of these, then you have to address the mail leaving from your IP and then contact them to be removed, just like a public blacklist. Almost all of them will automatically remove you eventually, but if you request delisting, it speeds up the process.
If you find yourself getting listed repeatedly, then you may want to contact one of our sales staff to hear how our services can eliminate this problem altogether. You can contact us at 866-MXTOOLBOX or sales@mxtoolbox.com
Peter
Peter
Product Development Engineer
peter@MXToolBox.com
512-637-8762