More and more I’m reading questions about finding and evaluating a new ESP, so I’ve reviewed a number of the answers and these links will be helpful in getting you through the process

* Competitive Analysis, Evaluating ESPs
* Switching Email Vendors
* Switching Email Vendors & Messing with Deliverability

If your looking for a new ESP you can find a very comprehensive list over at the Email Marketers Club Wiki; http://wiki.emailmarketersclub.com