What is Black-list? A Black-list is database of known Domains and IP addresses used by or for Spammers. A lot of Carriers/ISPs subscribe to these databases to spot and control SPAM from going across their links. Certain organizations will publish their Black-lists and allow you to search them to find out if you have been listed. Once you have been listed on one or two Black-lists, it will not be long before you are listed on all of the databases. Then you will not be able to send email to your customers or clients as they will be rejected due to Black-listing. How much time and money will your company lose due to this? There are numerous reasons why you might end up on a Black-list, a PC in your office might have been infected with a virus that sent out SPAM, a Marketing Email might have been falsely identified as SPAM or your email server might be open for relaying SPAM. Any number of these can end with being listed. Spf flattening What do you do now? Well, find the reason for the Black-listing for one. If it was an infected PC, then clean the virus off the computer and contact the Black-lists to be de-listed. Although, you have bigger issues than that because an infected PC could email out to the internet, which means that you have port 25 open to all traffic on your router or firewall. It should only be open for a specific device, your email server. If it was a Marketing Email, contact the Black-lists to be de-listed and check to see if you are Can-Spam compliant. Last but not least, the Open Relay on the email server should be disabled. There are several sites out there on the Net that will test your email server to see if it is Open to Relay. Take the necessary steps to secure the email server. Other items you might want to consider keeping this from happening again. An Email Security product will definitely help you from being Black-listed. From personal experience I would highly recommend IronPort. Since I have implemented this product, no more Black-listings, SPAM, or Virus emails have gotten through. IronPort is not the only product out on the market today; friends have recommended Barracuda products as well. Either way, you are protected.