The ease of use, customer service is outstanding as well all in one place for tracking purposes with your mailings which makes it easier to access at any time from anywhere without having to look up each individual carrier's website or call them directly. I am able to send out mass emails through this system that are easy to track down if there should be an issue later on when trying to find where they went wrong. It has been great so far but nothing really negative about using their services yet either just continue doing what you're already used too because everything seems fine thusfar. Tracking email campaigns sent via post office which allows me know exactly who received my campaign (i can see how many opened/unopened) along wth date recieved etc..