I have used the Act! Marketing Automation tool for quite a while now, and there were a lot of things that I liked about its e-mail campaign system. One of those things was the depth to which you can customize an action. If the email was opened you would send a different email. If it was not opened you would send a reminder. If the landing page was visited then you would do something else. If your team has never seen the Act! system, I would he happy to help with your research.
Overall, Act! was not great and was cumbersome. But there were some excellent tools in it.