The customer support is fantastic! They are always willing to help us with any questions we have. I've never had an issue that they haven't been able to answer in a timely manner. There is nothing really I can think of that I dislike about this tool. It's easy to set up, easy to use, and it does exactly what it says it will do. We're using MX Toolbox for blacklisting domains. Prior to using this service, we were experiencing issues with sending emails through our ISP. Using the filters provided