I read an interesting article on email metrics that I wanted to share with you. Standardized metrics are almost always an issue with various marketing modalities but I think email is particularly tough because there are so many measurement metrics. It is easy to measure one email against another internally, but comparing two different vendors can be a challenge.
The DMA is trying set an email marketing best practices standard to terms like Accepted, Bounce, and Click Through Rate. This is important because you may not currently be getting an apples-to-apples comparison due to ESPs measuring results differently.