It is amazing to see that so many marketers have not considered "intelligent business email" as a marketing channel. Most don't even know what it is in fact.
This keeps a log of how the space is developing. It will happen. It's a question of when.
Have a look at www.rocketseed.com as a starting point. They are the pioneers of the space.
Also worth a look at
Also www.forresterresearch.com has written a lot on this.