The ease of use, speed in testing emails through multiple platforms (SES). Also I like how many advanced features are there to test out so that you know your process works before sending live! I am not really disliking anything about this product but rather would like more control over my SMTP settings when using SPS/PowerDNS for example in order to test properly from one location or another without having issues later with DNS servers at work. Sending large amounts of Emails back & forth between our client sites as well as internal teams within those clients which helps us keep track of what's going along with each site/client we're working with. The ability to deliver emails from different sources, such as Gmail or Outlook, without any problems;The system has all the features I need and nothing that I don't like; It's reliable and easy to use;It saves time by automatically importing contacts into my database;PowerMailer works perfectly with our Exchange Server. Nothing at this moment. We are satisfied with the product but would like more options in case we have problems with it.