The GoodMessaging Project is a project which defines standards as to what makes a good e-mail. Anyone meeting those standards may display a GoodMessaging Compliance logo.
Both pieces of software and ISPs systems can be certified as GoodMessaging compliant
There are currently three levels of GoodMessaging compliance:
Obviously lots of room has been left for future improvements :).
Currently the project is in its initial phase. At the moment, the idea is to gather an interested group of people, and work on the specification.